java

Hibernate Interview Questions

2010-01-30T09:34:00.000-08:00

What is ORM ?

ORM stands for object/relational mapping. ORM is the automated persistence of objects in a Java application to the tables in a relational database.

What does ORM consists of ?

An ORM solution consists of the followig four pieces:
API for performing basic CRUD operations
API to express queries refering to classes
Facilities to specify metadata
Optimization facilities : dirty checking,lazy associations fetching

What are the ORM levels ?

The ORM levels are:
Pure relational (stored procedure.)
Light objects mapping (JDBC)
Medium object mapping
Full object Mapping (composition,inheritance, polymorphism, persistence by reachability)

What is Hibernate?

Hibernate is a pure Java object-relational mapping (ORM) and persistence framework that allows you to map plain old Java objects to relational database tables using (XML) configuration files.Its purpose is to relieve the developer from a significant amount of relational data persistence-related programming tasks.

Why do you need ORM tools like hibernate?

The main advantage of ORM like hibernate is that it shields developers from messy SQL. Apart from this, ORM provides following benefits:
Improved productivity
High-level object-oriented API
Less Java code to write
No SQL to write
Improved performance
Sophisticated caching
Lazy loading
Eager loading
Improved maintainability
A lot less code to write
Improved portability
ORM framework generates database-specific SQL for you

What Does Hibernate Simplify?

Hibernate simplifies:
Saving and retrieving your domain objects
Making database column and table name changes
Centralizing pre save and post retrieve logic
Complex joins for retrieving related items
Schema creation from object model

What are the most common methods of Hibernate configuration?

The most common methods of Hibernate configuration are:
Programmatic configuration
XML configuration (hibernate.cfg.xml)

What role does the Session interface play in Hibernate?

The Session interface is the primary interface used by Hibernate applications. It is a single-threaded, short-lived object representing a conversation between the application and the persistent store. It allows you to create query objects to retrieve persistent objects.

Session session = sessionFactory.openSession();

Session interface role:
Wraps a JDBC connection
Factory for Transaction
Holds a mandatory (first-level) cache of persistent objects, used when navigating the object graph or looking up objects by identifier

What role does the SessionFactory interface play in Hibernate?

The application obtains Session instances from a SessionFactory. There is typically a single SessionFactory for the whole application—created during application initialization. The SessionFactory caches generate SQL statements and other mapping metadata that Hibernate uses at runtime. It also holds cached data that has been read in one unit of work and may be reused in a future unit of work

SessionFactory sessionFactory = configuration.buildSessionFactory();

What is the general flow of Hibernate communication with RDBMS?

The general flow of Hibernate communication with RDBMS is :
Load the Hibernate configuration file and create configuration object. It will automatically load all hbm mapping files
Create session factory from configuration object
Get one session from this session factory
Create HQL Query
Execute query to get list containing Java objects

What is Hibernate Query Language (HQL)?

Hibernate offers a query language that embodies a very powerful and flexible mechanism to query, store, update, and retrieve objects from a database. This language, the Hibernate query Language (HQL), is an object-oriented extension to SQL.

How do you map Java Objects with Database tables?

First we need to write Java domain objects (beans with setter and getter).
Write hbm.xml, where we map java class to table and database columns to Java class variables.

Example :

name="userName" not-null="true" type="java.lang.String"/>
name="userPassword" not-null="true" type="java.lang.String"/>

What is the difference between and merge and update ?

Use update() if you are sure that the session does not contain an already persistent instance with the same identifier, and merge() if you want to merge your modifications at any time without consideration of the state of the session.

Define cascade and inverse option in one-many mapping?

cascade - enable operations to cascade to child entities.
cascade="all|none|save-update|delete|all-delete-orphan"

inverse - mark this collection as the "inverse" end of a bidirectional association.
inverse="true|false"
Essentially "inverse" indicates which end of a relationship should be ignored, so when persisting a parent who has a collection of children, should you ask the parent for its list of children, or ask the children who the parents are?

Define HibernateTemplate?

org.springframework.orm.hibernate.HibernateTemplate is a helper class which provides different methods for querying/retrieving data from the database. It also converts checked HibernateExceptions into unchecked DataAccessExceptions.

What are the benefits does HibernateTemplate provide?

The benefits of HibernateTemplate are :
HibernateTemplate, a Spring Template class simplifies interactions with Hibernate Session.
Common functions are simplified to single method calls.
Sessions are automatically closed.
Exceptions are automatically caught and converted to runtime exceptions.

How do you switch between relational databases without code changes?

Using Hibernate SQL Dialects , we can switch databases. Hibernate will generate appropriate hql queries based on the dialect defined.

If you want to see the Hibernate generated SQL statements on console, what should we do?

In Hibernate configuration file set as follows:
true

What are derived properties?

The properties that are not mapped to a column, but calculated at runtime by evaluation of an expression are called derived properties. The expression can be defined using the formula attribute of the element.

What are the Collection types in Hibernate ?

Bag
Set
List
Array
Map

What are the ways to express joins in HQL?

HQL provides four ways of expressing (inner and outer) joins:-
An implicit association join
An ordinary join in the FROM clause
A fetch join in the FROM clause.
A theta-style join in the WHERE clause.

Define cascade and inverse option in one-many mapping?

cascade - enable operations to cascade to child entities.
cascade="all|none|save-update|delete|all-delete-orphan"

inverse - mark this collection as the "inverse" end of a bidirectional association.
inverse="true|false"
Essentially "inverse" indicates which end of a relationship should be ignored, so when persisting a parent who has a collection of children, should you ask the parent for its list of children, or ask the children who the parents are?

What is Hibernate proxy?

The proxy attribute enables lazy initialization of persistent instances of the class. Hibernate will initially return CGLIB proxies which implement the named interface. The actual persistent object will be loaded when a method of the proxy is invoked.

How can Hibernate be configured to access an instance variable directly and not through a setter method ?

By mapping the property with access="field" in Hibernate metadata. This forces hibernate to bypass the setter method and access the instance variable directly while initializing a newly loaded object.

How can a whole class be mapped as immutable?

Mark the class as mutable="false" (Default is true),. This specifies that instances of the class are (not) mutable. Immutable classes, may not be updated or deleted by the application.

What is the use of dynamic-insert and dynamic-update attributes in a class mapping?

Criteria is a simplified API for retrieving entities by composing Criterion objects. This is a very convenient approach for functionality like "search" screens where there is a variable number of conditions to be placed upon the result set.
dynamic-update (defaults to false): Specifies that UPDATE SQL should be generated at runtime and contain only those columns whose values have changed
dynamic-insert (defaults to false): Specifies that INSERT SQL should be generated at runtime and contain only the columns whose values are not null.

What do you mean by fetching strategy ?

A fetching strategy is the strategy Hibernate will use for retrieving associated objects if the application needs to navigate the association. Fetch strategies may be declared in the O/R mapping metadata, or over-ridden by a particular HQL or Criteria query.

What is automatic dirty checking?

Automatic dirty checking is a feature that saves us the effort of explicitly asking Hibernate to update the database when we modify the state of an object inside a transaction.

What is transactional write-behind?

Hibernate uses a sophisticated algorithm to determine an efficient ordering that avoids database foreign key constraint violations but is still sufficiently predictable to the user. This feature is called transactional write-behind.

What are the types of Hibernate instance states ?

Three types of instance states:
Transient -The instance is not associated with any persistence context
Persistent -The instance is associated with a persistence context
Detached -The instance was associated with a persistence context which has been closed – currently not associated

What are the types of inheritance models in Hibernate?

There are three types of inheritance models in Hibernate:
Table per class hierarchy
Table per subclass
Table per concrete class

JDBC

2010-01-30T09:28:00.000-08:00

1 Q What is JDBC?
A
JDBC technology is an API (included in both J2SE and J2EE releases) that provides cross-DBMS connectivity to a wide range of SQL databases and access to other tabular data sources, such as spreadsheets or flat files. With a JDBC technology-enabled driver, you can connect all corporate data even in a heterogeneous environment

2 Q What are stored procedures?
A
A stored procedure is a set of statements/commands which reside in the database. The stored procedure is precompiled. Each Database has it's own stored procedure language,

3 Q What is JDBC Driver ?
A The JDBC Driver provides vendor-specific implementations of the abstract classes provided by the JDBC API. This driver is used to connect to the database.

4 Q What are the steps required to execute a query in JDBC?
A First we need to create an instance of a JDBC driver or load JDBC drivers, then we need to register this driver with DriverManager class. Then we can open a connection. By using this connection , we can create a statement object and this object will help us to execute the query.

5 Q What is DriverManager ?
A DriverManager is a class in java.sql package. It is the basic service for managing a set of JDBC drivers.

6 Q What is a ResultSet ?
A A table of data representing a database result set, which is usually generated by executing a statement that queries the database.

A ResultSet object maintains a cursor pointing to its current row of data. Initially the cursor is positioned before the first row. The next method moves the cursor to the next row, and because it returns false when there are no more rows in the ResultSet object, it can be used in a while loop to iterate through the result set.

7 Q What is Connection?
A Connection class represents a connection (session) with a specific database. SQL statements are executed and results are returned within the context of a connection.

A Connection object's database is able to provide information describing its tables, its supported SQL grammar, its stored procedures, the capabilities of this connection, and so on. This information is obtained with the getMetaData method.

8 Q What does Class.forName return?
A A class as loaded by the classloader.

9 Q What is Connection pooling?
A Connection pooling is a technique used for sharing server resources among requesting clients. Connection pooling increases the performance of Web applications by reusing active database connections instead of creating a new connection with every request. Connection pool manager maintains a pool of open database connections.

10 Q What are the different JDB drivers available?
A There are mainly four type of JDBC drivers available. They are:

Type 1 : JDBC-ODBC Bridge Driver - A JDBC-ODBC bridge provides JDBC API access via one or more ODBC drivers. Note that some ODBC native code and in many cases native database client code must be loaded on each client machine that uses this type of driver. Hence, this kind of driver is generally most appropriate when automatic installation and downloading of a Java technology application is not important. For information on the JDBC-ODBC bridge driver provided by Sun.

Type 2: Native API Partly Java Driver- A native-API partly Java technology-enabled driver converts JDBC calls into calls on the client API for Oracle, Sybase, Informix, DB2, or other DBMS. Note that, like the bridge driver, this style of driver requires that some binary code be loaded on each client machine.

Type 3: Network protocol Driver- A net-protocol fully Java technology-enabled driver translates JDBC API calls into a DBMS-independent net protocol which is then translated to a DBMS protocol by a server. This net server middleware is able to connect all of its Java technology-based clients to many different databases. The specific protocol used depends on the vendor. In general, this is the most flexible JDBC API alternative. It is likely that all vendors of this solution will provide products suitable for Intranet use. In order for these products to also support Internet access they must handle the additional requirements for security, access through firewalls, etc., that the Web imposes. Several vendors are adding JDBC technology-based drivers to their existing database middleware products.

Type 4: JDBC Net pure Java Driver - A native-protocol fully Java technology-enabled driver converts JDBC technology calls into the network protocol used by DBMSs directly. This allows a direct call from the client machine to the DBMS server and is a practical solution for Intranet access. Since many of these protocols are proprietary the database vendors themselves will be the primary source for this style of driver. Several database vendors have these in progress.

11 Q What is the fastest type of JDBC driver?
A
Type 4 (JDBC Net pure Java Driver) is the fastest JDBC driver. Type 1 and Type 3 drivers will be slower than Type 2 drivers (the database calls are make at least three translations versus two), and Type 4 drivers are the fastest (only one translation).

12 Q Is the JDBC-ODBC Bridge multi-threaded?
A
No. The JDBC-ODBC Bridge does not support multi threading. The JDBC-ODBC Bridge uses synchronized methods to serialize all of the calls that it makes to ODBC. Multi-threaded Java programs may use the Bridge, but they won't get the advantages of multi-threading.

13 Q What is cold backup, hot backup, warm backup recovery?
A
Cold backup means all these files must be backed up at the same time, before the database is restarted. Hot backup (official name is 'online backup' ) is a backup taken of each tablespace while the database is running and is being accessed by the users

14 Q
What is the advantage of denormalization?
A
Data denormalization is reverse procedure, carried out purely for reasons of improving performance. It maybe efficient for a high-throughput system to replicate data for certain data.

15 Q How do you handle your own transaction ?
A Connection Object has a method called setAutocommit ( boolean flag) . For handling our own transaction we can set the parameter to false and begin your transaction . Finally commit the transaction by calling the commit method.

ERP Interview Questions

2010-01-30T08:57:00.000-08:00

What is ERP?

ERP is an acronym that stands for Enterprise Resource Planning. ERP is package software solution that addresses the enterprise needs of an organization by tightly integrating the various functions of an organization using a process view of the organization. It is a package software and not a custom made software for a specific firm. It understands the needs of any organization within a specific industry segment. Many of the processes implemented in an ERP software are core processes such as order processing, order fulfillment, shipping, invoicing, BOM processing, purchase order processing, preparation of Balance Sheet, Profit and Loss statement etc., that are common to all industry segments. That is the reason why the package software solution works so well. The firm specific needs are met through a process of customization. ERP addresses not merely the needs of a single function such as finance, marketing, production or HR. Rather it addresses the entire needs of an enterprise that cuts across these functions to meaningfully execute any of the core processes. ERP integrates the functional modules tightly. It is not merely the import and export of data across the functional modules. The integration ensures that the logic of a process that cuts across the function is captured genuinely. This in turn implies that data once entered in any of the functional modules (whichever of the module owns the data) is made available to every other module that needs this data. This leads to significant improvements by way of improved consistency and integrity of data. ERP users the process view of the organization in the place of function view which dominated the enterprise software before the advent of ERP. The process view provides a much better insight into the organizational systems and procedures and also breaks the "kingdoms" that work at cross-purposes in many organizations. To implement such a demanding software one needs high performance computing, high availability systems, large, high speed high availability on line storage and high speed, high reliable net works, all at affordable cost. Though many ERP software vendors have been around for more than two decades, ERP software started to make major inroads into the corporate world only in the last couple of years. Interestingly Indian corporate houses are taking the ERP route exceptionally fast, even by world standards in the past two years. The investments on a complete ERP implementation for a Rs. 100+ core corporation would easily run into Rs 10+ crores. ERP is the only software whose deployment decisions are made in the corporate boardrooms and not by EDP / MIS departments. ERP software today represents possibly the single most expensive piece of general-purpose software.

Why ERP?

Corporations go for ERP either to solve the existing problems or to explore new opportunities. I call these two approaches as negative & positive approach respectively. One aspect of the negative approach forces some corporations to go for ERP to solve their Y2K problem. This is particularly true of those corporations that are heavily dependent on legacy systems running on old main frames. The second aspect of the negative approach is to get over the problems of islands of heterogeneous and incompatible information systems that were developed over the past several years in many organizations. Functional IS modules representing areas such as Finance, Marketing, HR, and Production in these organizations would be running on diverse hardware and software platforms leading to nearly insurmountable problems of reconciling data locked up among the diverse systems. From a positive perspective many organization look at the great opportunity provided by ERP software that lead to almost instant access of transactional information across the corporation. Such an information rich scenario permits organization to reduce inventory across multiple units/ departments/ plants; reduce cycle times from weeks to hours; and improve customer satisfaction by orders of magnitude. All these translate to increased profitability or increase in market share and in turn much larger market capitalization. However ERP is only means and not an end by itself. ERP provides an opportunity for a corporation to operate as an agile entity to improve production / operation, customer service and customer satisfaction. The creative ingenuity of an organization to drive towards these corporate goals determines the extent of success an ERP implementation can deliver.

Does can packaged software fit business needs well?

Many IS professionals perceive ERP as a paradox. "How can a software company located in Germany, Netherlands or U.S.A understand the needs of my organization operating in Bangalore?" is the question they generally ask. Many of them feel that custom software should work far better than packaged software. For many of them holding this view, the success of ERP is a paradox. What they miss out is the point that the core processes of most organizations are by and large, the same. Thanks to globalization, there has been a significant amount of uniformity, standardization and simplification of the core processes across the industry. Some of the technologies such as EDI have even standardized the contents of critical documents, such as shipping and purchase orders. Standard processes and procedures, for example, Letter of Credit, have seen a great level of standardization to suit International Trade. These developments permit companies in Germany and Netherlands to develop the world-class software that can be profitably used by a corporation in Bangalore also. By pumping in billions of dollars in understanding the business processed used by thousands of corporations worldwide, the ERP software vendors also bring in world-class practices to any company that implements the ERP software. In a similar vein, large ERP software vendors such as SAP & BaaN are also able to employ and retain thousands of software professionals who can continuously improve their ERP software product. No individual end user company can afford such large pool of software professionals. This is the secret of success of ERP. A possible analogy may drive home the point better. An average Indian has already realized the fact that a ready-made garment made using sophisticated technology can indeed fit him/her better than a street corner tailor. The highly sophisticated technology of Computer Aided Design to model human anatomy and Computer Aided Manufacturing tools to cut complex contours effortlessly at high speed, explain the better fit. Similar is the case of packaged software.

Do we get best business practices through ERP?

The answer to this question is Yes and No. ERP software like SAP R/3 or RAMCO Marshal has the benefit of understanding the best practices followed in thousands of corporations worldwide, where the particular ERP software has been implemented. In a sense, ERP software embeds these best practices inside their software. This explains the Yes part of the answer. One reason why end users pay an exorbitant amount to buy ERP software is the fact that ERP is not just a piece of "shrink wrapped" software. The embedded business processes inside provide the real value to the ERP software. So, ERP can bring "best of the breed" practices to any organization. However, the onus of profiting through these best practices entirely lies on the end users. An organization suffering from " Not invented here" syndrome may do too much over customization and build into ERP implementation the archaic practices followed for decades in a specific company. This in turn may deprive the benefits of the best practices to that company. This explains the No part of the answer.

{For core Business Processes it may be the best to follow the best business practices of the ERP vendor, but there is always a percentage of customization required for any ERP implementation. The ability of the ERP to extend easily is a critical factor to evaluate.}

How are ERP & BPR related?

BPR as an acronym stands for Business Process Reengineering. It used to be a buzzword until a few years ago. Overzealous BPR pundits caused so much havoc through job cuts, it is a controversial subject today in many countries. An organization can go for standalone BPR or they can choose ERP. Since ERP anyway comes bundled with several of the best practices, a well implemented ERP exercise leads to some amount of BPR, though the reengineering effort may not be full-blown. However, reengineering through ERP, generally termed package enabled process reengineering (PEPR) leads to less drastic change in an organization. Such package enabled reengineering through ERP has been received much better by the end users rather than stand alone BPR in many companies around the world.

Should BPR & ERP be taken in any order?

There is no easy algorithm that can give a simple answer. A BPR exercise preceding the ERP implementation can help the organization significantly. It may also increase a combined time of implementing BPR and ERP significantly. There is also a risk that a particular ERP software selected later may not be able to implement the reengineered processes. A simultaneous BPR and ERP exercise saves time and also minimizes the risk of sequential implementation of BPR followed by ERP. One rarely comes across the instance where BPR is followed by ERP. As such the ordering of ERP & BPR must be based on the needs of a specific organization.

What are the typical modules of ERP?

Typical Modules of ERP include sales (sales forecasting, customer prospecting, customer follow-up, support for telemarketing, database marketing), order processing (inquiry handling, order taking) shipping, transportation, invoicing, finance (G/L, AR, AP), asset management, cost accounting, financial accounting, manufacturing and materials management. Optionally quality project, warehouse, continuos production and other modules are also present in different ERP software. Industry specific modules to cater to hospitals, retail, banking, insurance, oil, shipping and transportation are also available from some vendors.

Why is top management commitment necessary for the success of ERP?

ERP will ultimately affect everyone in the organization. An ERP implementation represents a major organizational intervention. The process view of ERP would remove many of the "kingdoms" in the organization. This would lead to a shift in power centers; naturally ERP represents a major change. Managing change of such high order cannot be done without top management commitment. ERP exercise is also a major exercise and can cost anyway from several lakhs to several crores of rupees. Such large resource requirements also necessitate commitment from top management. Last, but not the least, ERP implementation is a long process, generally running into several months. Keeping an activity alive for such long duration would be nearly impossible without top management commitment.

What is top management commitment in ERP Context?

The top management commitment in ERP is not limited to writing a big cheque, which is very much necessary. But it has to go much beyond that. ERP exercise in India represents a paradigm shift in the way many CEO's run their corporations. ERP software implementation vendors often make it mandatory for the chief executive and his / her team to spend a full one week listening to ERP consultants. Such an exercise is unheard of at least in the Indian corporate history. The core committee of ERP needs champions who are well respected, very knowledgeable and often impossible to spare for any organization. The success of ERP implementation needs the full-time attention of these champions who must be drawn from the key functions and detained for ERP project implementation for a long period of six to nine months. ERP project cannot be managed by people who "can be spared"; it must be managed by the "indispensable" personnel. Top Management commitment must ensure the release of such key people for the ERP core committee. The ERP software often brings the best practices from the industry. To benefit from such best practices, existing business practices may have to be altered. Top management commitment should include the political will to implement such changes.

Why is change management necessary for ERP?

ERP being a major initiative costing significant amount of money, lasting several months and ultimately affecting everyone in the organization, change management is the key for the success of any ERP project. ERP software brings along with them some of the best practices. Implementing such practices would need change. To profit from ERP such change must be managed. That is the reason ERP needs top management commitment.

Is ERP too expensive for Indian Companies?

It is a loaded question. The cost of ERP software should not be viewed as an expense. It is an investment towards an ability that provides better profitability, market share or customer service. Of course, the up-front cost of ERP software is very high. Most software pieces used by the corporations for commercial applications never had price tags of crores of rupees which ERP software carry. ERP decisions are a "high-risk high reward" decision. The view that ERP is expensive only looks at the risk but not the rewards.

What are the special challenges of ERP introduction in India?

The challenges of introduction of ERP in India are in general the same as in other countries. This includes change management, organizational intervention, shifting from function view to process view and faith in package software in the place of custom-built software. The special challenges in India arise from the existence of large IS shops inside many Indian corporations who may view ERP as a threat to their very existence. The Indian software companies also see a threat to their project-based software business in ERP. Traditionally organizations in India depended more on IS professionals rather than business professionals for commercial software developments. ERP places more value on domain knowledge of the functions rather than IT skills. This calls for a mind-set change, which is a challenge. Last, but not the least, is the lack of communication infrastructure, which is often necessary to implement ERP. The IT infrastructure needed for ERP implementation is orders of magnitude more than the infrastructure needed for the legacy application. This again calls for a mindset change.

How do you cost justify ERP?

It is difficult to calculate return on investment for ERP decisions, though several successful installations of ERP had dramatic returns on investment. For example, Microsoft estimates that the investments in ERP will be paid back by way of better performance in flat two years. It must be realized that the ERP is an enabler. ERP gives agility to organization, which can be exploited to improve profitability, market share or customer service. Without ERP, the organization may not be in a position to handle larger business or provide faster response to customers. The results from enlarged business or faster customer response should pay back for ERP investment. It is predicated on the fact that the organization would leverage the agility towards such corporate goals. ERP helps in pursuing such goals often successfully. But mere ERP implementation does not necessarily translate to benefits. Better health enables a human being to do things, which would have been difficult, if not impossible, without such sound health. But if the individual does not make use of his improved status towards the pursuit of any goal, he or she is not capitalizing on the improved health. ERP must also be viewed as a way of providing a better health to an organization.

Does ERP leads to unemployment?

This is a loaded question. Today, a large number of middle managers, supervisory staff etc, are busy chasing information, making queries, preparing reports and checking or verifying compliance to simple rules. It could be the preparation of the list of employees who are due for retirement next year or verifying whether an applicant for earned leave has enough leave to his credit. With a successful ERP in place, information will be freely available and any casual user can very easily generate any ad hoc queries or reports. The system will automatically check for the compliance for most of the standard rules. As such, a number of routine jobs will disappear. However, with the information system in place, many of the middle level managers can be empowered to perform far more interesting analysis, develop insights and suggest innovative schemes for improvement. Often these are the real benefits are ERP. If an organization is not imaginative enough to empower people to perform such analysis, obviously ERP can be discredited with creating unemployment. The Computerized Railway Reservation System in India may serve as a good example. With the networked computer terminals, one can manage the issuing of the tickets with fewer staff. However, today we have more railway reservation clerks than what we had ten years back. The average counter hours across the country have increased from 6 hours a day to 12 hours per day. We are able to cope with much larger number of passengers, thanks to the population growth. An average user is also able to make reservations from "any place to any place" from any one of the terminals, significantly improving service quality. In a way Railway Reservation System has taken away a few jobs but created many more jobs. In all such cases looking at the head count may be an incorrect way to approach the problem. The goal must be to provide better quality service and better quality of jobs.

What is the contribution to ERP from India?

The most valuable contribution to ERP has been the launch of the world class ERP Product Marshall from Ramco Systems. Developed in late 80's using the technology of the 80's (unlike many other ERP Products, which use 70's technology), Marshall is a visionary product and represents the first successful large-scale software product from India. Hopefully India will also contribute to courseware development and supply quality manpower to the world at large. BaaN has plans to do considerable product development from its Hyderabad Development Center. Over the years world-class ERP software development may happen right in the country.

What is the ERP life cycle?

The set of activities through which ERP is implemented in an organization constitutes the ERP life cycle. This can be compared to the well developed System Development Life Cycle (SDLC) in the traditional Structured System Analysis and Design (SSAD). Typical ERP project consists of the following steps:

Step 1: ERP readiness assessment

Step 2: Preparing the organization for ERP

Step 3: ERP Feasibility Study

Step 4: Process modelling and documenting the "AS IS" processes & "TO BE" processes (along with BPR)

Step 5: Detailed plan for ERP implementation (includes ERP software selection, selection of implementation partners, implementation methodology - "Big Bang" or Modular Implementation - and the final and precise extent of implementation)

Step 6: Detailed implementation including development, quality assurance and production system

Step 7: Preparing to "go live" including data migration

Step 8: Going live

Step 9: Performance assessment, documentation, training (continues in early stages also) and future plans.

Is there a good time to "go live"?

Yes. Most implementations of ERP include financial module. Every organization has a financial (fiscal) year both for internal use as well as far legal / governmental consolidation. Since the account books must be closed and financial reports prepared (including the balance sheet and the profit and loss statement) for the financial year, most ERP implementations try to synchronize their "go live" date with that of the financial year. (April 1 in India). If for some reason it cannot be on (April 1), many organizations "go live" on October 1 at the end of the half-year. Technically ERP software doesn't impose any restrictions. Any day is good enough to "go live" as long as it is not " tomorrow"!

Why do ERP consultants charge a high fee?

ERP consultants operate in the "high risk high reward" area. Contemporary ERP software are complex pieces which need years to master. ERP consultants invest significant amount of time and effort, which need to be rewarded. ERP Consultancy is also given to the highest levels of management often at the level of CEO. CEO level consulting cannot come cheap. A well-implemented ERP can translate to crores of rupees of saving for an organization justifying once again the high cost of ERP consultants. ERP consultants also combine a rare combination of communication skill, domain knowledge and software expertise, once again justifying the high cost. Last, but not the least, ERP sales are growing fast and the demand for ERP consultants is all time high. The gap in supply-demand also explains the unusually high cost of ERP consultants.

What is the special role of Big Six consultants - Who are they?

The Big Six Consulting houses are Anderson consulting, Ernst & Young, Price Waterhouse, Coopers & Lybrand, KPMG and Delolite & Touche. With the recent merger of Price Water House and C & L into PWC the big six will become big five from July 15th 1998. All of them are actively engaged in ERP consulting. PWC's ERP business will be the largest in the world with over 9,800 consultants. Over the years, the big six consultants have accumulated probably the richest ERP implementation experiences through thousands of ERP installations worldwide. Almost all of them have developed their own methodologies of implementation that add significant value to the ERP software. Many of them have full-fledged development centers, labs, proof of concept centers and competency centers in many countries around the world. These centers offer environments for potential clients to test run, fine tune and simulate their implementations. The consultants also have developed excellent course-ware and training materials of immense value in the ERP area. In short the big six consultants are the "bells and whistles" of ERP industry.

What is the role of process-modeling tools ERP implementation?

Process Modelling provides a means to map the organization processes and visualize it in a graphical manner. This helps in communication, clarification and documentation of the "AS IS" and "TO BE" processes. Process modelling can be used to reinforce the central theme of ERP, namely, a shift from function orientation to process orientation.

What is the role of process-modeling tools ERP implementation?

How do you decide a fit between an organization and ERP software?

There is no precise algorithm that can measure the fit for an organization to particular ERP software. One generally goes by experiences of similar organizations that have implemented ERP. In general, every ERP software has exceptional strengths in some area. It is better to stay with that ERP software which has special strengths for your area. For example, BaaN & Oracle have outstanding manufacturing modules; People Soft and Marshall have outstanding HR modules. If your core business centers around one of these modules your choice becomes easier. An academic way to evaluate the fit is to carefully study all the business processes that characterize your business and to look for matching business processes that are supported by particular ERP software. Often such an exercise would call for several man-years of effort. The skill set needed for such an exercise may not be easily available within the organization. Getting an outside consulting group to do this exercise may be very expensive. Often most organizations decide the ERP software vendor based on the broad needs of the industry in which they operate and the support offered by particular ERP software for that industry.

What is the drawback of over customization?

Customization is the process of fitting the chosen ERP software to the needs of a specific organization. Whenever the processes represented in the ERP software differ significantly from the processes used by the firm one has two options. First is to build the organizational process into the ERP software through customization. The second one is to change the practice followed by the firm to suit the process native to the ERP software. Traditional common sense would force people to customize the software to suit the individual demands of the organization. This leads to two problems. The first one arises out of the fact that any customization done locally is outside the core ERP software. Accordingly, the next release of the ERP software would not support local customization. They have to be re-done by the end user for the new release. Second the very purpose of ERP is to take advantage of the best practices in industry that come embedded with the ERP software. By over customizing the implementers would deprive the benefit of world - class practice to the organization that is implementing ERP.

Who are the key ERP Software vendors in the world?

How are they positioned in India? All the key players in the ERP global market are practically present in India. This includes SAP with their flagship product R/3, BaaN Company with their BaaN IV product, Oracle with their Oracle Applications and the world-class ERP Product Marshall from the rising Indian star Ramco Systems. The other major player in the global ERP Market, namely, PeopleSoft has entered the Indian market only very recently. Yet another leading product MFG/ PRO from QAD has been present for a while (the two customers Hindustan Lever & Godrej have been using it for over two years). SAP has been exceptionally successful in India with nearly two-thirds of the Indian market share. The major industrial houses Tata, Reliance, Essar, Mahindra & Kirloskar have embraced SAP. BaaN has been very successful in major manufacturing companies such as TVS. Oracle has been a playing a dominant role in the telecom centre with a stronghold among all cellular phone companies. Ramco Marshall has a good client base among the process industry in the south and a few public sector undertakings. (The detailed list of ERP installations in India).

What is the secret of success of SAP?

SAP is a visionary company that could visualize the emergence of ERP twenty years back. Its flagship product R/3 also capitalized the client-server technology in late 80's, which was the right time to leverage client-server technology for mission critical applications. Both these points put together gave SAP a formidable early-bird advantage. The majority of the "top ten" companies (classified using every measure - annual turnover, profitability or market capitalization) in the world are with SAP today. Many leading companies such as Microsoft in software, Intel in microprocessor, IBM, HP, Compaq & Digital (today only Compaq) in computer industry are with SAP. Naturally, SAP not only has a large market share but also the "mind share" of the users. With increase in globalization of the large companies, the corporate decision of a company to go for SAP automatically translates to SAP installation in dozens, if not hundreds of the subsidiaries of the parent organization. This keeps SAP growing continuously. The "strategic selling" concept perfected by SAP keeps its partners happy all the time. For every dollar which SAP earns, its partners (implementation partners such as the "big six" consulting firms, hardware partners such as Compaq and software partners such as Microsoft) earn five dollars! Naturally the partners keep recommending SAP to all their clients. SAP's absence from "direct consulting" has indirectly helped SAP. The "big six" in particular have been extremely supportive of SAP. SAP's sales pitch has been more business oriented than technology oriented. SAP should be given the special credit for taking the software decisions to the boardroom. SAP style of selling the ERP concept to senior-most executives of the corporation (including the chief executive) often bypassing the MIS departments, is unprecedented in software selling. By a process of certification of every component involved in ERP - servers, operating systems, DBMS, Consultants and even installers of the software - SAP has created a strong brand loyalty and premium quality image. By restricting and closely monitoring access to training through its Partner academy, SAP has created a high-class of Certified Consultants who demand extremely high premium. Until recently SAP did not permit any one, other than its partners, to offer training on SAP products. This created scarcity of trained consultant, which in turn increased the market value of the consultant. This point alone has resulted in unrealistic ambitions amongst potential consultants. Teaching shops exploit this unrealistic expectation. Fuelling on each other, the trainee consultants & training houses almost enacted the drama of the "Californian gold rush" in the last few months. The recent Hyderabad incident is one such manifestation of this bizarre scheme.

What are the special features of SAP R/3?

SAP R/3 addresses the enterprise needs of typical large scale manufacturing and trading organizations. SAP R/3 product is ideally suited for large corporations that have multiple products, manufactured out of multiple plants, often distributed across multiple continents and countries. R/3 can handle multiple currencies, multiple language scripts and multiple accounting systems, multiple valuation schemes and multiple depreciation schemes exceptionally well. SAP R/3 also has outstanding consolidation schemes for holding companies and other complex organization structures. In the current days of mergers and accusations this point becomes particularly relevant for large corporations. SAP R/3 probably has the largest number of features among all ERP software products, though many of them remain unused often. Special versions focussed on specific needs are also available in the form of industry solutions (IS) for retail, banking, oil & gas, hospitals etc. SAP R/3 support the full N-Tier Client- Server Architecture that scales exceptionably well. It is also the only software that runs on widest range of hardware platforms, namely, CISC & RISC based processors from Intel, IBM, Sun, Digital, MIPS etc., AS/400 and IBM main frames. It also can support operating systems ranging from Unix (several versions from HP, Sun, IBM, Digital and SGI), Windows NT, OS/400 etc., It also supports multiple RDBMS including DB2 from IBM, Oracle, Informix and Microsoft SQL server. Naturally, there is a price the users pay for all these features. The software is complex and difficult to master. The system is rigid and forces the organizations to change their internal processes (though it ultimately benefits the users). The implementation takes a long time. The consultants charge a high fee. The software needs significantly larger resources in terms of processing power, disk space and network speed.

What are the special features of Oracle Applications?

Oracle Applications evolved from Oracle financials an outstanding product. Since Oracle has an exceptionally high acceptance of its RDMBS product, Enterprise users were already Oracle users for a much longer time. A very large number of SAP installations use Oracle DBMS to support SAP R/3. Oracle also has an excellent manufacturing module in the form of Oracle manufacturing. As can be expected from an outstanding software company, Oracle Apps also has a superior GUI user interface compared to the prosaic interfaces of SAP or BaaN. Oracle has strong client base among manufacturing industry and financial services industry. Utilities and telecom companies are other strongholds of Oracle. Practically every cellular phone company in India is an Oracle client. Oil and Gas Industry is another focus area where Oracle is exceptionally strong.

What are the special features of BaaN?

BaaN Company is driven by innovation. It is a pure-breed client-server company whose products were available only in the Unix platform for many years. Today BaaN products run on multiple hardware and software platforms. The focused development of BaaN has led to several technological strengths for BaaN products. Very few companies commit and deliver software products, whose code length decreases with the new release of their product. BaaN is definitely one of them. Their software is exceptionally strong in manufacturing. The software is much less complex, far easy to master, for less expensive to implement and permits a faster implementation. Another dimension of BaaN's innovation is their tool Dynamic Enterprise Modeler (DEM) which permits a model-based implementation of the BaaN IV product. BaaN can run under modest computing resources suiting the SME sector very well. The recent announcements from BaaN about the use of component based software engineering tools (using Microsoft DCOM technology), tight integration with Microsoft BackOffice, component based licensing through its innovative BaaN Series product scheme etc show great promise.

What are special features of Ramco Marshall?

A World-class product from India in a true Swadeshi sprit from Ramco Systems has a lot of promise. Endorsed by none other than Bill Gates himself, Marshall is a true versionary product. Marshal has the advantage of exploiting the great strides made in software engineering in 80's. Being wedded to Microsoft and Intel for processor architectuire, Operating systems and DBMS (Intel processor based servers, Windows NT server O/S, & SQL Server) Marshal is an extremely focused product. This in turn leads to better performance, simplicity of design and ultimately reduced cost of ownership for Marshall customers. These late-comer advantages also imply the disadvantages such as blessings from the big six consultants, lack of implementation methodology and inflexibility in hardware & software platforms choice.

{Implementation methodology is present in the form of RSPRINT - Ramco Stratagic Program for Implementation and Training. A process model of Ramco Marshall is also currently ready which will be used for implementation . Big 6 blessings not there because we do the implementations ourselves, and this will be there the moment we achieve the critical mass. Inflexibility in platform choice, but being wedded to Microsoft allows us to ride the Microsoft wave. Oracle Apps also do not have RDBMS choice. Most hardware companies today support NT and hence database is the only limitaion.}

Is there a specific place for IBM?

IBM should get a special place in the ERP arena. A couple of ex- IBM engineers originally designed a piece of software that ultimately became SAP R/3. But for the development of IBM Main frames, IBM's DB2 DBMS and many other tools, ERP as it is known today would not have been possible. However as in many other instances IBM could not directly benefit from its own development (The story of IBM PC, IBM printers, IBM DOS, IBM Windows etc., is no different.)

Who is the market leader in ERP?

Undoubtedly SAP is the market leader in ERP and has almost one-third the market share. Interestingly SAP has captured two thirds of the market share in India though ERP business is less than two years old in India.

{2/3rds of market share in terms of revenues but not number of sites/organizations}

Is there a segmentation of the ERP market?

There is no easy way to segment the ERP market in a precise manner that can be readily adopted by an organization as a thumb rule. However SAP R/3, Oracle Applications, BaaN Series, People Soft & Ramco Marshall represent the high-end of the ERP market. SSA BBCS & JD Edwards represent the medium-end market. Scala, Intentia Movex & QAD MFG / PRO represent the low-end of the market. This division is generally based on past installation, pricing and positioning of the products by the ERP vendors themselves. It does not necessarily mean that low end products lack features or high end products have all features. It may be instructive to note that a large company HLL uses QAD MFG/PRO (a low end ERP) and a small company Microland uses SAP R/3 (a high end ERP).

Is there a rating agency that constantly rates ERP software?

A number of independent consulting firms have been providing white papers that document strengths and weakness of the leading software products both from technology and market perspectives. These include Gartner group, Yankee group, Meta group and AMS, to name a few leading consulting firms. Gartner group annual ERP market white paper is the most authoritative document describing the relative strengths of the leading edge ERP software products. This document gets updated once every quarter.

Where do you get ERP software market information?

Once again Gartner group and IDC, Data Quest are the prime sources of ERP market related information. India specific information is made available by IDC India.

What R & D do ERP vendors attempt?

The research and development by the ERP vendors is both in the technology and application perspective. The application groups continuously monitor improved business practices of the leading edge corporations, new business practices pioneered by innovative upcoming companies and re-engineer business process from process modelling consultants. At the technology level ERP vendors continue their support for promising and upcoming technologies such as object technologies distributed components messaging standards, multimedia support, multi processor support, next generation processors, operating systems, databases and networking technologies.

Is there a benchmarking tool to fine tune ERP performance?

Every ERP vendor provides performance guidelines that can be used by system administrators to fine tune performance. Some of them are very comprehensive and address fine-tuning at the application, database, operating system, processor and even the network level. Other ERP vendors provide tools that can leverage the leading edge database tuning, operating system tuning and network performance tuning tools.

Is ERP too expensive for Indian Companies?

What are the special challenges of ERP introduction in India?

Does ERP leads to unemployment?

What is the contribution to ERP from India?

{By 80's technology does it mean technology created in research labs in the80's or technology commercially available in the 80's. If it means commercially available, Ramco Marshall is on 90's technology currently}

What is meant by India version of specific ERP software?

ERP software must address all the enterprise needs of an organization within the social context in which the enterprise operates. This would imply that the local accounting practices, locally applicable taxation laws (excise, customs, sales tax and income tax) are fully adhered to in implementing the various business processes. The software vendor must incorporate India specific features before selling the software. The specific ERP software that has been adopted to suit to Indian statutory laws is called India specific ERP.

Should I go for ERP training?

This is a difficult question to answer and there is no clear yes or no answer to this question. It all depends on what you want achieve in your life, your background, your skills and the market in which you plan to operate. If you have communication skills, domain knowledge in key organizational functions (sales, manufacturing, materials, distribution, accounting, finance, HR etc or in areas such as quality, project or costing) and software skills with one of the leading ERP software, you will have a great time with possible assignments that will reward you with attractive compensation. This assumes that you are willing to look at the global market. If you have specific experience and knowledge in any of the key industry segments such as oil, finance, telecom, distribution, retailing, banking, hospitals, etc, it will be very useful. However deficiency even in one of the key segments is likely to hurt. If you are an MCA or B.E. or B.Tech. in computer science and fresh from the college, discount heavily the rosy pictures painted by the street corner training shops. ERP consulting or training does not need enormous computing skills. As such, non-engineers such as accountants, lawyer's etc can also make a career in ERP provided they have a good understanding of the organizational systems and processes, computer literacy and willingness to change.

How to get ERP training?

The ERP vendors and their implementation partners deliver most of the ERP training. There are several levels of training. Overview training in ERP concepts and ERP benefits would be necessary for the top management and steering committee members. An in depth software specific training would be necessary for the implementation team. An infrastructure management (hardware, software, networking) and ERP software maintenance training would be necessary for the IT team. Once implemented, detailed user-training would be necessary for a large number of users and potential users throughout the organization. User training would be limited to modules specific to individual users.

What is the ideal background for ERP Consultants?

An ideal background of ERP Consultants would be several years of domain knowledge (HR, Finance, Material etc) followed by extensive software training and implementation experience with at least a couple of real-world implementations. Technical knowledge by way of deep IT training helps but not mandatory. Knowledge of business process by way of formal business school education, once again is of help but not necessary. However business knowledge by the way of experience and consulting is a must.

What is customization in ERP?

Customization is the job of fitting the ERP software to meet the demands of a particular organization. This would mean the mapping of the organizational structures, processes & environment of the organization into the corresponding model of the organization that is embedded in the ERP software. In other words, it is a mapping of the real world into the model world of the particular ERP software. The structure and processes represent one part of customization; the creation of master data, input-output forms, validations, reports, queries, formats, authorization, backup / restore procedures, data administration procedures, disaster recovery processes etc., represent the full gamut of customization.

What is the ERP life cycle?

Step 1: ERP readiness assessment

Step 2: Preparing the organization for ERP

Step 3: ERP Feasibility Study

Step 4: Process modelling and documenting the "AS IS" processes & "TO BE" processes (along with BPR)

Step 6: Detailed implementation including development, quality assurance and production system

Step 7: Preparing to "go live" including data migration

Step 8: Going live

Step 9: Performance assessment, documentation, training (continues in early stages also) and future plans.

Is there a good time to "go live"?

What is the role of implementation partner?

Implementation partners generally come from specialized ERP consulting houses that are generally outside the organization. Being experts in a particular area (materials, production, finance or distribution), these experts from outside, not only bring software expertise with respect to particular ERP software, but also bring the extra benefit from their vast prior experiences in other firms where they would have implemented that particular ERP. Over the years, the implementation partners have developed enough know-how in the form of templates for implementation. These templates significantly reduce the cost and time of implementation and errors of implementation. Though implementation consultants charge a high fee, they bring significant amount of value, thanks to their prior experiences.

Why do ERP consultants charge a high fee?

What is the role of process-modeling tools ERP implementation?

What is the drawback of over customization?

What are the three dominant approaches to ERP implementation?

The three dominant approaches to ERP implementation are "big bang", location-wise and module-wise implementation. In the big bang approach the organization decides to implement all relevant modules, for example - Financials, Logistics & HR- all at the same time. This has the advantage of getting the full benefit of the integrated software across all functions of the organization. However there is a risk of the implementation getting out of control. In "Location-wise" implementation, the organization chooses a specific location, say, the head office, one of the new plants etc. The choice could be based on better infrastructure, better IT culture, more co-operative set of users, higher level of automation etc. In "module-wise" implementation individual modules are taken up for implementation in a phased manner depending on the criticality of applications. Once again a module taken up for implementation can be implemented across all locations or just one location. Later they can be rolled out to other locations.

What is 'big bang' approach to ERP?

This has already been explained elsewhere. See previous answer.

ERP being integrated software does one benefit by implementing only specific modules?

Yes. The full benefit of ERP would accrue if all the ERP modules are implemented. However many organizations implement ERP only in those functions, which are, considered to be of strategic importance. Some of the modules, though they appear to be limited to specific functions, in fact integrate with many other functions indirectly. For example finance module primarily targets the accounting and finance functions. However the accounts payable module address all the material purchases and in turn impacts the entire materials management functions. Many more examples can be quoted to reinforce our viewpoint. The process orientation of ERP software definitely contributes to a better management of the organization. Even partial implementation of the ERP therefore leads to significant benefits.

Why are "financials", the first module implemented in many Indian ERP implementations?

Financial modules provide the basic pulse of an organization. It also impacts all other modules. Successful implementations of financials show up immediately reinforcing the faith of an organization in ERP. Other modules cannot be implemented without the financial module in place. All these factors explain the fact that financial modules are taken up first.

Why do consultants recommend changing business practice to suit the ERP software rather than customizing the software to every user needs?

A key contribution of ERP software is the bundled business process knowledge that come along with ERP software. These processes have evolved over the past two decades of ERP implementation in some of the most well-managed corporations around the world. By adapting to those processes that have proved successful in some of the finest corporations around the world, an organization implementing ERP would get the advantage of these "best of the breed" practices. That is the reason behind the consultant recommendations.

I have a large MIS department with outstanding programmers and analysis - Should I create my own ERP?

Unless your line of Business is so unusual that no existing ERP software available in the market meets your needs you should not attempt to develop your own ERP software. The reason why ERP software has been so successful is due to the deficiencies of software developed in house by MIS departments. IS/IT staff who generally constitutes the MIS department lack business and process orientation. The success of ERP is due to the fact that ERP software development teams have business knowledge. In house software development has also proved to be more costly and time consuming compared to the implementation of packaged ERP software. No MIS department can afford to hire hundreds, if not thousands of professionals dedicated to software development. You should attempt ERP software development only if you want to address the general business needs of an enterprise through a standard ERP software product, not to meet the requirements of your organization. As you can readily see these are entirely different games. A software giant Microsoft decided to use SAP R/3 rather than develop it in-house!

Is there a benchmarking tool to fine tune ERP performance?

How to prepare an organization for ERP implementation?

There is no easy magic through which one can prepare an organization for ERP implementation. Exposing the top management to the benefits of ERP through the real world case studies, sharing of experience by other corporations that have successfully implemented ERP and creation of awareness is the first step. Convincing the top management to use a high risk, high reward scheme such as ERP is a major challenge. Almost all the members of the organization should get the excitement about ERP project implementation. Communicating and sharing of the ERP vision is the most important organizational preparation for a successful ERP implementation.

What is an ERP Project team?

ERP project team would be charged with the responsibility of implementing the ERP for the specific organization. A champion, who is skilled in communication and understands the organization well should head the ERP team. The leader must be well accepted by the most employees of the organization. The leader also must be a person who can keep the motivation level of the implementation team at fairly high levels throughout the several months of implementation. The implementation team would consist of dozens of people. There will be a number of teams for each of the functional area with every team consisting of key users and IT personnel to provide technology support.

Who are the project champions?

Project champions (for the crore processes that are taken up for implementation) would be those individuals who would take the ownership of implementation. They are expected to provide the leadership so as to sustain the trials and tribulations of ERP implementation.

What does "going live" mean?

After many months of implementation plan every organization would decide a particular date when they would shift from their legacy system to the ERP system. Up to that time the ERP software would be under development followed by testing and quality assurance. Once by ERP implementation team feels convinced that the development is complete and testing is satisfactory, they would decide to "go live". In a sense "go live" date marks the end of ERP project completion. Generally most ERP project "go live" on the starting of the fiscal/ financial year, namely April 1 in India.

How is "data migration" managed for ERP implementation?

To complete the ERP implementation one would need to migrate master data, including customer master, material master, budget head, employee list etc from legacy systems. Large number of earlier transaction (pending transaction for completion, archived transaction for analysis) would also be transported to the ERP system. In a typical corporation these would call for significant amount of data transport. Often they many not be available in machine-readable form. Often manual data will have inconsistencies such as incorrect code numbers, multiple code numbers to represent the same item, misspellings etc that needs data cleansing. Data cleansing itself could be a major activity. Even if data is available in machine-readable form, it may be distributed across heterogeneous hardware and software platforms. Reasonable amount of effort must be spent in reconciling such data. Special utilities are available for data migration both from ERP vendors and third party vendors. For the Indian IT industry data migration itself could be a major business opportunity.

For ERP implementation across multiple location does one need dedicated communication channels like leased lines/ V SAT terminals?

Many ERP implementation sites that are geographically distributed need reliable communication links for on-line transaction processing. In the absence of public data network in India, most organizations are forced to go for VSAT networks and leased line circuits in India.

What is the main reason for end users accepting ERP?

ERP speaks the end user language more than any other software piece. ERP implementation had been successful whenever it was driven by business goals and not IT goals. ERP vendors have been successful in convincing the end users to take ERP decisions. Rarely IT departments take the decision to go far ERP. The ERP training and skills to use ERP can be developed by end users quite easily. All these together have generated substantial user acceptance of ERP.

ERP Related Conferences

Most of the ERP conferences are specific to products. This include SAPHIRE for SAP (held many times a year in all the continents), BaaN World held twice a year for BaaN, Oracle World for Oracle Apps and the recently started Ramco Conference (Marshal in the New Millennium), QAD Conference. BMA / CSI / IIMB conference ERP98 held early this year in Bangalore is a trailblazer in India. It was followed by two such conferences hosted by Media Transasia.

Research Institutions working on ERP IIM, Bangalore has a well established ERP Studies Center with initial funding from SAP / Intel / Compaq. BaaN Institute in Hyderabad, SP Jain Instiute in Bombay, NITIE in Bombay, PSG Tech in Coimbatore and are the other Institutions with focussed groups working in the ERP area. IIT Delhi & IIM Calcutta are in the process of establishing ERP Centers.

How much does it cost to go for ERP?

The cost of ERP project would vary significantly from one instance to other. The actual cost depends on the nature of the industry, the size of the firm, the geographical distribution of the organizational units such as offices, plants, warehouses and distribution points, the number of user licenses and the extent of ERP implementation (the number of functional modules implemented). A typical mid-size Indian company with about Rs 100- 300 crores of annual business will have to invest about five to twenty crores of rupees in the ERP project. This includes ERP software licenses, server cost, communication network cost and the cost of consultants who would do the implementation. Large corporations with Rs 1000+ crores of annual business might invest Rs 100+ crores in ERP project. A number of small companies have managed to implement ERP in about Rs 1 crore. It may be noted here that in a typical installation the cost of ERP software accounts for only about 20% of the overall cost. A major component in ERP project is the cost of the implementation consultant (both internal and external).

What is ERP?

ERP stands for “enterprise resource planning”. The definition of enterprise resource planning is an integrated software solution used to manage a company’s resources. ERP systems integrate all business management functions, including planning, inventory/materials management, engineering, order processing, manufacturing, purchasing, accounting and finance, human resources, and more.

Why implement an ERP system?

ERP software integrates all departments and functions across a company onto a single computer system that can serve all those different departments' particular needs. ERP combines finance, HR, manufacturing and distribution all together into a single, integrated software program that runs off a single database so that the various departments can more easily share information and communicate with each other. This integrated approach can have a tremendous payback provided the software is installed and used correctly.

What are the benefits of an ERP System?

The benefits derived from ERP can far outweigh the costs of the system, providing that the system is selected carefully and is appropriate for your company from a feature, cost, and technology standpoint. Some of the benefits realized are:

A single integrated system

Streamlining processes and workflows

Reduce redundant data entry and processes

Establish uniform processes that are based on recognized best business practices

Information sharing across departments

Improved access to information

Improved workflow and efficiency

Improved customer satisfaction based on improved on-time delivery, increased Quality, shortened delivery times

Reduced inventory costs resulting from better planning, tracking and forecasting of reQuirements

Turn collections faster based on better visibility into accounts and fewer billing and/or delivery errors

Decrease in vendor pricing by taking better advantage of Quantity breaks and tracking vendor performance

Track actual costs of activities and perform activity based costing

Provide a consolidated picture of sales, inventory and receivables

An ERP system provides the solid operational backbone manufacturers and distributors need to improve the volume of production and fulfillment of orders while reducing costs. By optimizing your manufacturing and distribution operations with ERP, you'll also be able to focus on new business opportunities.

Data Warehousing Interview questions

2010-01-30T08:38:00.000-08:00

Data Warehousing Interview questions

What is Data warehousing?
A data warehouse can be considered as a storage area where interest specific or relevant data is stored irrespective of the source. What actually is required to create a data warehouse can be considered as Data Warehousing. Data warehousing merges data from multiple sources into an easy and complete form.
Data warehousing is a process of repository of electronic data of an organization. For the purpose of reporting and analysis, data warehousing is used. The essence concept of data warehousing is to provide data flow of architectural model from operational system to decision support environments.

What are fact tables and dimension tables?
As mentioned, data in a warehouse comes from the transactions. Fact table in a data warehouse consists of facts and/or measures. The nature of data in a fact table is usually numerical.
On the other hand, dimension table in a data warehouse contains fields used to describe the data in fact tables. A dimension table can provide additional and descriptive information (dimension) of the field of a fact table.
e.g. If I want to know the number of resources used for a task, my fact table will store the actual measure (of resources) while my Dimension table will store the task and resource details.
Hence, the relation between a fact and dimension table is one to many.
Business facts or measures and foreign keys are persisted in fact tables which are referred as candidate keys in dimension tables. Additive values are usually provided by the fact tables which acts as independent variables by which dimensional attributes are analyzed.
Attributes that are used to constrain and group data for performing data warehousing queries are persisted in the dimension tables.

What is ETL process in data warehousing?
ETL is Extract Transform Load. It is a process of fetching data from different sources, converting the data into a consistent and clean form and load into the data warehouse. Different tools are available in the market to perform ETL jobs.
ETL stands for Extraction, transformation and loading. That means extracting data from different sources such as flat files, databases or XML data, transforming this data depending on the application’s need and loads this data into data warehouse.

Explain the difference between data mining and data warehousing.
Data warehousing is merely extracting data from different sources, cleaning the data and storing it in the warehouse. Where as data mining aims to examine or explore the data using queries. These queries can be fired on the data warehouse. Explore the data in data mining helps in reporting, planning strategies, finding meaningful patterns etc.
E.g. a data warehouse of a company stores all the relevant information of projects and employees. Using Data mining, one can use this data to generate different reports like profits generated etc.
Data mining is a method for comparing large amounts of data for the purpose of finding patterns. Data mining is normally used for models and forecasting. Data mining is the process of correlations, patterns by shifting through large data repositories using pattern recognition techniques.
Data warehousing is the central repository for the data of several business systems in an enterprise. Data from various resources extracted and organized in the data warehouse selectively for analysis and accessibility.

What is an OLTP system and OLAP system?
OLTP: Online Transaction and Processing helps and manages applications based on transactions involving high volume of data. Typical example of a transaction is commonly observed in Banks, Air tickets etc. Because OLTP uses client server architecture, it supports transactions to run cross a network.
OLAP: Online analytical processing performs analysis of business data and provides the ability to perform complex calculations on usually low volumes of data. OLAP helps the user gain an insight on the data coming from different sources (multi dimensional).
OLTP stands for OnLine Transaction Processing. Applications that supports and manges transactions which involve high volumes of data are supported by OLTP system. OLTP is based on client-server architecture and supports transactions across networks.
OLAP stands for OnLine Analytical Processing. Business data analysis and complex calculations on low volumes of data are performed by OLAP. An insight of data coming from various resources can be gained by a user with the support of OLAP.

What are cubes?
A data cube stores data in a summarized version which helps in a faster analysis of data. The data is stored in such a way that it allows reporting easily.
E.g. using a data cube A user may want to analyze weekly, monthly performance of an employee. Here, month and week could be considered as the dimensions of the cube.
Multi dimensional data is logically represented by Cubes in data warehousing. The dimension and the data are represented by the edge and the body of the cube respectively. OLAP environments view the data in the form of hierarchical cube. A cube typically includes the aggregations that are needed for business intelligence queries.

What is snow flake scheme design in database?
A snowflake Schema in its simplest form is an arrangement of fact tables and dimension tables. The fact table is usually at the center surrounded by the dimension table. Normally in a snow flake schema the dimension tables are further broken down into more dimension table.
E.g. Dimension tables include employee, projects and status. Status table can be further broken into status_weekly, status_monthly.
Snow flake schema is one of the designs that are present in database design. Snow flake schema serves the purpose of dimensional modeling in data warehousing. If the dimensional table is split into many tables, where the schema is inclined slightly towards normalization, then the snow flake design is utilized. It contains joins in depth. The reason is that, the tables split further.

What is analysis service?
Analysis service provides a combined view of the data used in OLAP or Data mining. Services here refer to OLAP, Data mining.
An integrated view of business data is provided by analysis service. This view is provided with the combination of OLAP and data mining functionality. Analysis Services allows the user to utilize a wide variety of data mining algorithms which allows the creation and designing data mining models.
Explain sequence clustering algorithm.
Sequence clustering algorithm collects similar or related paths, sequences of data containing events.
E.g. Sequence clustering algorithm may help finding the path to store a product of “similar” nature in a retail ware house.
Explain discrete and continuous data in data mining.
Discreet data can be considered as defined or finite data. E.g. Mobile numbers, gender.
Continuous data can be considered as data which changes continuously and in an ordered fashion. E.g. age.
Finite data can be considered as discrete data. For example, employee id, phone number, gender, address etc.
If data changes continually, then that data can be considered as continuous data. For example, age, salary, experience in years etc.

Explain time series algorithm in data mining.
Time series algorithm can be used to predict continuous values of data. Once the algorithm is skilled to predict a series of data, it can predict the outcome of other series.
E.g. Performance one employee can influence or forecast the profit

What is XMLA?
XMLA is XML for Analysis which can be considered as a standard for accessing data in OLAP, data mining or data sources on the internet. It is Simple Object Access Protocol. XMLA uses discover and Execute methods. Discover fetched information from the internet while Execute allows the applications to execute against the data sources.
XMLA stands for XML for Analysis. It is an industry standard for accessing data in analytical systems, such as OLAP. XMLA is based on XML, SOAP and HTTP.
Explain the difference between Data warehousing and Business Intelligence.
Data Warehousing helps you store the data while business intelligence helps you to control the data for decision making, forecasting etc.
Data warehousing using ETL jobs, will store data in a meaningful form. However, in order to query the data for reporting, forecasting, business intelligence tools were born.
The management of different aspects like development, implementation and operation of a data warehouse is dealt by data warehousing. It also manages the meta data, data cleansing, data transformation, data acquisition persistence management, archiving data.
In business intelligence the organization analyses the measurement of aspects of business such as sales, marketing, efficiency of operations, profitability, and market penetration within customer groups. The typical usage of business intelligence is to encompass OLAP, visualization of data, mining data and reporting tools.

What is Dimensional Modeling?
Dimensional modeling is often used in Data warehousing. In simpler words it is a rational or consistent design technique used to build a data warehouse. DM uses facts and dimensions of a warehouse for its design. A snow and star flake schema represent data modeling.
Dimensional modeling is one of the logical design techniques used in data warehousing. It is different from entity-relationship model. If applied to relational databases, and done properly, it is 2nd or 3rd normal form. It does not necessarily involve relational database. The logical level of modeling approach can be applied in physical form like database tables or flat files. It is one of the techniques for the support of end-user queries in data warehousing. On contrary to database administration, it is oriented around understandability.

What is surrogate key? Explain it with an example.
Data warehouses commonly use a surrogate key to uniquely identify an entity. A surrogate is not generated by the user but by the system. A primary difference between a primary key and surrogate key in few databases is that PK uniquely identifies a record while a SK uniquely identifies an entity.
E.g. an employee may be recruited before the year 2000 while another employee with the same name may be recruited after the year 2000. Here, the primary key will uniquely identify the record while the surrogate key will be generated by the system (say a serial number) since the SK is NOT derived from the data.
A surrogate key is a unique identifier in database either for an entity in the modeled word or an object in the database. Application data is not used to derive surrogate key. Surrogate key is an internally generated key by the current system and is invisible to the user. As several objects are available in the database corresponding to surrogate, surrogate key can not be utilized as primary key.
For example, a sequential number can be a surrogate key.

What is the purpose of Factless Fact Table?
Fact less tables are so called because they simply contain keys which refer to the dimension tables. Hence, they don’t really have facts or any information but are more commonly used for tracking some information of an event.
Eg. To find the number of leaves taken by an employee in a month.
A tracking process or collecting status can be performed by using fact less fact tables. The fact table does not have numeric values that are aggregate, hence the name. Mere key values that are referenced by the dimensions, from which the status is collected, are available in fact less fact tables.

What is a level of Granularity of a fact table?
A fact table is usually designed at a low level of Granularity. This means that we need to find the lowest level of information that can store in a fact table.
E.g. Employee performance is a very high level of granularity. Employee_performance_daily, employee_perfomance_weekly can be considered lower levels of granularity.
The granularity is the lowest level of information stored in the fact table. The depth of data level is known as granularity. In date dimension the level could be year, month, quarter, period, week, day of granularity.
The process consists of the following two steps:
- Determining the dimensions that are to be included
- Determining the location to place the hierarchy of each dimension of information
The factors of determination will be resent to the requirements.

Explain the difference between star and snowflake schemas.
A snow flake schema design is usually more complex than a start schema. In a start schema a fact table is surrounded by multiple fact tables. This is also how the Snow flake schema is designed. However, in a snow flake schema, the dimension tables can be further broken down to sub dimensions. Hence, data in a snow flake schema is more stable and standard as compared to a Start schema.
E.g. Star Schema: Performance report is a fact table. Its dimension tables include performance_report_employee, performance_report_manager
Snow Flake Schema: the dimension tables can be broken to performance_report_employee_weekly, monthly etc.
Star schema: A highly de-normalized technique. A star schema has one fact table and is associated with numerous dimensions table and depicts a star.
Snow flake schema: The normalized principles applied star schema is known as Snow flake schema. Every dimension table is associated with sub dimension table.
Differences:
A dimension table will not have parent table in star schema, whereas snow flake schemas have one or more parent tables.
The dimensional table itself consists of hierarchies of dimensions in star schema, where as hierarchies are split into different tables in snow flake schema. The drilling down data from top most hierarchies to the lowermost hierarchies can be done.
A snowflake schema is a more normalized form of a star schema. In a star schema, one fact table is stored with a number of dimension tables. On the other hand, in a star schema, one dimension table can have multiple sub dimensions. This means that in a star schema, the dimension table is independent without any sub dimensions.

What is the difference between view and materialized view?
A view is created by combining data from different tables. Hence, a view does not have data of itself.
On the other hand, Materialized view usually used in data warehousing has data. This data helps in decision making, performing calculations etc. The data stored by calculating it before hand using queries.
When a view is created, the data is not stored in the database. The data is created when a query is fired on the view. Whereas, data of a materialized view is stored.
View:
Tail raid data representation is provided by a view to access data from its table.
It has logical structure can not occupy space.
Changes get affected in corresponding tables.
Materialized view
Pre calculated data persists in materialized view.
It has physical data space occupation.
Changes will not get affected in corresponding tables.

What is a Cube and Linked Cube with reference to data warehouse?
A data cube stores data in a summarized version which helps in a faster analysis of data. Where as linked cubes use the data cube and are stored on another analysis server. Linking different data cubes reduces the possibility of sparse data.
E.g. A data cube may store the Employee_performance. However in order to know the hours which calculated this performance, one can create another cube by linking it to the root cube (in this case employee_performance).
Logical data representation of multidimensional data is depicted as a Cube. Dimension members are represented by the edge of cube and data values are represented by the body of cube.
Linked cubes are the cubes that are linked in order to make the data remain constant.

What is junk dimension?
In scenarios where certain data may not be appropriate to store in the schema, this data (or attributes) can be stored in a junk dimension. The nature of data of junk dimension is usually Boolean or flag values.
E.g. whether the performance of employee was up to the mark? , Comments on performance.
A single dimension is formed by lumping a number of small dimensions. This dimension is called a junk dimension. Junk dimension has unrelated attributes. The process of grouping random flags and text attributes in dimension by transmitting them to a distinguished sub dimension is related to junk dimension.

What are fundamental stages of Data Warehousing?
Stages of a data warehouse helps to find and understand how the data in the warehouse changes.
At an initial stage of data warehousing data of the transactions is merely copied to another server. Here, even if the copied data is processed for reporting, the source data’s performance won’t be affected.
In the next evolving stage, the data in the warehouse is updated regularly using the source data.
In Real time Data warehouse stage data in the warehouse is updated for every transaction performed on the source data (E.g. booking a ticket)
When the warehouse is at integrated stage, It not only updates data as and when a transaction is performed but also generates transactions which are passed back to the source online data.
Offline Operational Databases: This is the initial stage of data warehousing. In this stage the development of database of an operational system to an off-line server is done by simply copying the databases.
Offline Data warehouse: In this stage the data warehouses are updated on a regular time cycle from operational system and the data is persisted in an reporting-oriented data structure.
Real time Data Warehouse: Data warehouses are updated based on transaction or event basis in this stage. An operational system performs a transaction every time.
Integrated Data Warehouse: The activity or transactions generation which are passed back into the operational system is done in this stage. These transactions or generated transactions are used in the daily activity of the organization.

What is Virtual Data Warehousing?
The aggregate view of complete data inventory is provided by Virtual Warehousing. The metadata is utilized for forming logical enterprise data model which is a part of database of record infrastructure , is contained in virtual data warehousing. The infrastructure consists of publishments of legacy database sysems with their metadta extracted. The standards JEE, JMS and EJBs are used in the infrastructure for the purpose of transactional unit requests and extract-tranform-load tools are used for loading real time bulk data.
A virtual data warehouse provides a compact view of the data inventory. It contains Meta data. It uses middleware to build connections to different data sources. They can be fast as they allow users to filter the most important pieces of data from different legacy applications.

What is active data warehousing?
The transactional data captured and reposited in the Active Data Warehouse. This repository can be utilized in finding trends and patterns that can be used in future decision making.
An Active data warehouse aims to capture data continuously and deliver real time data. They provide a single integrated view of a customer across multiple business lines. It is associated with Business Intelligence Systems.

List down differences between dependent data warehouse and independent data warehouse.
Dependent data ware house are build ODS,where as independent data warehouse will not depend on ODS.
A dependent data warehouse stored the data in a central data warehouse. On the other hand independent data warehouse does not make use of a central data warehouse.

What is data modeling and data mining? What is this used for?
Designing a model for data or database is called data modelling. Data is reposited in fact table and dimension table. Fact table consists of data about transaction and dimensional table consists of master data. Data model is used to design abstract model of database.
The process of obtaining the hidden trends is called as data mining. Data mining is used to transform the hidden into information. Data mining is also used in a wide range of practicing profiles such as marketing, surveillance, fraud detection.
Data modeling aims to identify all entities that have data. It then defines a relationship between these entities. Data models can be conceptual, logical or Physical data models. Conceptual models are typically used to explore high level business concepts in case of stakeholders. Logical models are used to explore domain concepts. While Physical models are used to explore database design.
Data mining is used to examine or explore the data using queries. These queries can be fired on the data warehouse. Data mining helps in reporting, planning strategies, finding meaningful patterns etc. it can be used to convert a large amount of data into a sensible form.

Difference between ER Modeling and Dimensional Modeling.
Dimensional modelling is very flexible for the user perspective. Dimensional data model is mapped for creating schemas. Where as ER Model is not mapped for creating shemas and does not use in conversion of normalization of data into denormalized form.
ER Model is utilized for OLTP databases that uses any of the 1st or 2nd or 3rd normal forms, where as dimensional data model is used for data warehousing and uses 3rd normal form.
ER model contains normalized data where as Dimensional model contains denormalized data.
ER modeling that models an ER diagram represents the entire businesses or applications processes. This diagram can be segregated into multiple Dimensional models. This is to say, an ER model will have both logical and physical model. The Dimensional model will only have physical model.

What is snapshot with reference to data warehouse?
A snapshot of data warehouse is a persisted report from the catalogue. The persistence into a file is done after disconnecting report from the catalogue.
A snapshot is in a data warehouse can be used to track activities. For example, every time an employee attempts to change his address, the data warehouse can be alerted for a snapshot. This means that each snap shot is taken when some event is fired.
A snapshot has three components –
Time when event occurred.
A key to identify the snap shot.
Data that relates to the key.

What is degenerate dimension table?
The dimensions that are persisted in the fact table is called dimension table. These dimensions does not contain its own dimensions. Mapping does not take place for the columns available in fact tables. The values in the table is neither dimensions nor measures.
A degenerate table does not have its own dimension table. It is derived from a fact table. The column (dimension) which is a part of fact table but does not map to any dimension.
E.g. employee_id

What is Data Mart?
Data Mart is a data repository which is served to a community of people who works on knowledge (also known as knowledge workers). The data resource can be from enterprise resources or from a data warehouse.
Data mart stores particular data that is gathered from different sources. Particular data may belong to some specific community (group of people) or genre. Data marts can be used to focus on specific business needs.

What is the difference between metadata and data dictionary?
Metadata describes about data. It is ‘data about data’. It has information about how and when, by whom a certain data was collected and the data format. It is essential to understand information that is stored in data warehouses and xml-based web applications.
Data dictionary is a file which consists of the basic definitions of a database. It contains the list of files that are available in the database, number of records in each file, and the information about the fields.
Data dictionary is a repository to store all information. Meta data is data about data. Meta data is data that defines other data. Hence, the data dictionary can be metadata that describes some information about the database.

Describe the various methods of loading Dimension tables.
The following are the methods of loading dimension tables:
Conventional Load:
In this method all the table constraints will be checked against the data, before loading the data.
Direct Load or Faster Load:
As the name suggests, the data will be loaded directly without checking the constraints. The data checking against the table constraints will be performed later and indexing will not be done on bad data.
The methods to load Dimension tables:
Conventional load:- Here the data is checked for any table constraints before loading.
Direct or Faster load:- The data is directly loaded without checking for any constraints.

What is the difference between OLAP and data warehouse?
The following are the differences between OLAP and data warehousing:
Data Warehouse
Data from different data sources is stored in a relational database for end use analysis.
Data organization is in the form of summarized, aggregated, non volatile and subject oriented patterns.
Supports the analysis of data but does not support data of online analysis.
Online Analytical Processing
With the usage of analytical queries, data is analyzed and evaluated in the data ware house.
Data aggregation and summarization is utilized to organize data using multidimensional models.
Speed and flexibility for online data analysis is supported for data analyst in real time environment.
A data warehouse serves as a repository to store historical data that can be used for analysis. OLAP is Online Analytical processing that can be used to analyze and evaluate data in a warehouse. The warehouse has data coming from varied sources. OLAP tool helps to organize data in the warehouse using multidimensional models.

Describe the foreign key columns in fact table and dimension table.
The primary keys of entity tables are the foreign keys of dimension tables.
The Primary keys of fact dimensional table are the foreign keys of fact tables.
A foreign key of a fact table references other dimension tables. On the other hand, dimension table being a referenced table itself, having foreign key reference from one or more tables.

What is cube grouping?
A transformer built set of similar cubes is known as cube grouping. A single level in one dimension of the model is related with each cube group. Cube groups are generally used in creating smaller cubes that are based on the data in the level of dimension.

Define the term slowly changing dimensions (SCD).
Slowly changing dimension target operator is one of the SQL warehousing operators that can be used in mining flow or in data flow.
When the attribute for a record varies over time, the SCD is applied.
SCD are dimensions whose data changes very slowly. An example of this can be city of an employee. This dimension will change very slowly. The row of this data in the dimension can be either replaced completely without any track of old record OR a new row can be inserted, OR the change can be tracked.

What is a Star Schema?
The simplest data warehousing schema is star schema. It consists of fact tables that refer any number of dimension tables. It is the special case schema to be considered for snowflake schema.
In a star schema comprises of fact and dimension tables. Fact table contains the fact or the actual data. Usually numerical data is stored with multiple columns and many rows. Dimension tables contain attributes or smaller granular data. The fact table in start schema will have foreign key references of dimension tables.
Differences between star and snowflake schema.
Star Schema: A de-normalized technique in which one fact table is associated with several dimension tables. It resembles a star.
Snow Flake Schema: A star schema that is applied with normalized principles is known as Snow flake schema. Every dimension table is associated with sub dimension table.

Explain the use of lookup tables and Aggregate tables.
At the time of updating the data warehouse, a lookup table is used. When placed on the fact table or warehouse based upon the primary key of the target, the update is takes place only by allowing new records or updated records depending upon the condition of lookup.
The materialized views are aggregate tables. It contains summarized data. For example, to generate sales reports on weekly or monthly or yearly basis instead of daily basis of an application, the date values are aggregated into week values, week values are aggregated into month values and month values into year values. To perform this process @aggregate function is used.
An aggregate table contains summarized view of data. Lookup tables, using the primary key of the target, allow updating of records based on the lookup condition.

What is real time data-warehousing?
The combination of real-time activity and data warehousing is called real time warehousing. The activity that happens at current time is known as real-time activity. Data is available after completion of the activity.
Business activity data is captured in real-time data warehousing as the data occurs. Soon after the business activity and the available data, the data of completed activity is flown into the data warehouse. This data is available instantly. Real-time data warehousing can be viewed / utilized as a framework for the information retrieval from data as the data is available.
In real time data-warehousing, the warehouse is updated every time the system performs a transaction. It reflects the businesses real time information. This means that when the query is fired in the warehouse, the state of the business at that time will be returned.

What is conformed fact? What is conformed dimensions use for?
Allowing having same names in different tables is allowed by Conformed facts. The combining and comparing facts mathematically is possible.
A dimensional table can be used more than one fact table is referred as conformed dimension. It is used across multiple data marts along with the combination of multiple fact tables. Without changing the metadata of conformed dimension tables, the facts in an application can be utilized without further modifications or changes.
Conformed fact in a warehouse allows itself to have same name in separate tables. They can be compared and combined mathematically. Conformed dimensions can be used across multiple data marts. These conformed dimensions have a static structure. Any dimension table that is used by multiple fact tables can be conformed dimensions.

Define non-additive facts.
The facts that can not be summed up for the dimensions present in the fact table are called non-additive facts. The facts can be useful if there are changes in dimensions. For example, profit margin is a non-additive fact for it has no meaning to add them up for the account level or the day level.
Non additive facts are facts that cannot be summed up for any dimensions present in fact table. This means that these columns cannot be added for producing any results.

Define BUS Schema.
A BUS schema is to identify the common dimensions across business processes, like identifying conforming dimensions. BUS schema has conformed dimension and standardized definition of facts.
List out difference between SAS tool and other tools.
The differences between SAS and other tools are:
-SAS is a reporting tool.
-SAS is an ETL tool and also a forecasting tool.
Tools other than SAS
- consists of reporting tool, for example, Business Objects Cognos or ETL tool, for example, Informatica, or both , for example Business Objects.
Other tools does not have forecasting tool. For this reason, SAS is used in most in Clinical Trials and health care industry.
SAS provides more features in comparison to other tools. it supports almost ALL database interfaces and has its own extensive database engine.

Why is SAS so popular?
Statistical Analysis System is an integration of various software products which allows the developers to perform
Data entry, data retrieval, data management and data mining
Report writing and supports for graphics
Statistical analysis, business planning, business forecasting and business decision support
Operations research and project management, quality improvement, application development
Extract, transform and load functions in data warehousing.
Platform independent and remote computing
Because of these many features, SAS has become more and more popular.
SAS is an ETL tool. Not just this it can be used for reporting and can be used for forecasting business needs.

What is data cleaning? How can we do that?
Data cleaning is also known as data scrubbing. Data cleaning is a process which ensures the set of data is correct and accurate. Data accuracy and consistency, data integration is checked during data cleaning. Data cleaning can be applied for a set of records or multiple sets of data which need to be merged.
Data cleaning is performed by reading all records in a set and verifying their accuracy. Typos and spelling errors are rectified. Mislabeled data if available is labeled and filed. Incomplete or missing entries are completed. Unrecoverable records are purged, for not to take space and inefficient operations.
Data cleaning is the process of identifying erroneous data. The data is checked for accuracy, consistency, typos etc.
Methods:-
Parsing - Used to detect syntax errors.
Data Transformation - Confirms that the input data matches in format with expected data.
Duplicate elimination - This process gets rid of duplicate entries.
Statistical Methods- values of mean, standard deviation, range, or clustering algorithms etc are used to find erroneous data.

Explain in brief about critical column.
A column (usually granular) is called as critical column which changes the values over a period of time.
For example, there is a customer by name ‘Anirudh’ who resided in Bangalore for 4 years and shifted to Pune. Being in Bangalore, he purchased Rs. 30 Lakhs worth of purchases. Now the change is the CITY in the data warehouse and the purchases now will shown in the city Pune only. This kind of process makes data warehouse inconsistent. In this example, the CITY is the critical column. Surrogate key can be used as a solution for this.
A critical column in a warehouse is a column whose value changes over a period of time. For e.g. city of the user. If a user resides in city 'abc' and the warehouse keeps a track of his per day expenses - when the user changes the city, the data warehouse becomes inconsistent since the city has changed and the expenses are shown under the new city.

What is data cube technology used for?
Data cube is a multi-dimensional structure. Data cube is a data abstraction to view aggregated data from a number of perspectives. The dimensions are aggregated as the ‘measure’ attribute, as the remaining dimensions are known as the ‘feature’ attributes. Data is viewed on a cube in a multidimensional manner. The aggregated and summarized facts of variables or attributes can be viewed. This is the requirement where OLAP plays a role.
Data cubes are commonly used for easy interpretation of data. It is used to represent data along with dimensions as some measures of business needs. Each dimension of the cube represents some attribute of the database. E.g Sales per day, month or year.

What is Data Scheme?
Data Scheme is a diagrammatic representation that illustrates data structures and data relationships to each other in the relational database within the data warehouse.
The data structures have their names defined with their data types.
Data Schemes are handy guides for database and data warehouse implementation.
The Data Scheme may or may not represent the real lay out of the database but just a structural representation of the physical database.
Data Schemes are useful in troubleshooting databases.

What is Bit Mapped Index?
Bitmap indexes make use of bit arrays (bitmaps) to answer queries by performing bitwise logical operations.
They work well with data that has a lower cardinality which means the data that take fewer distinct values.
Bitmap indexes are useful in the data warehousing applications.
Bitmap indexes have a significant space and performance advantage over other structures for such data.
Tables that have less number of insert or update operations can be good candidates.
The advantages of Bitmap indexes are:
They have a highly compressed structure, making them fast to read.
Their structure makes it possible for the system to combine multiple indexes together so that they can access the underlying table faster.
The Disadvantage of Bitmap indexes is:
The overhead on maintaining them is enormous.

What is Bi-directional Extract?
In hierarchical, networked or relational databases, the data can be extracted, cleansed and transferred in two directions. The ability of a system to do this is refered to as bidirectional extracts.
This functionality is extremely useful in data warehousing projects.
Data Extraction
The source systems the data is extracted from vary in various forms right from their structures and file formats to the department and the business segment they belong to. Common source formats include flat files and relational database and other non-relational database structures such as IMS, VSAM or ISAM.
Data transformation
The extracted data may undergo transformation with possible addition of metadata before they are exported to another large storage area.
In transformation phase, various functions related to business needs, requirements, rules and policies are applied on them. During this process some values even get translated and encoded. Care is also taken to avoid redundancy of data.
Data Cleansing
In data cleansing, scrutinizing of the incorrect or corrupted data is done and those inaccuracies are removed. Thus data consistency is ensured in Data cleansing.
It involves activities like
- removing typographical errors and inconsistencies
- comparing and validating data entries against a list of entities
Data transformation
This is the last process of Bidirectional Extracts. The cleansed, transformed extracted source data is then loaded into the data warehouse.
Advantages
- Updates and data loading become very fast due to bidirectional extracting.
- As timely updates are received in a useful pattern companies can make good use of this data to launch new products and formulate market strategies.
Disadvantage
- More investment on advance and faster IT infrastructure.
- Not being able to come up with fault tolerance may mean unexpected stoppage of operations when the system breaks.
- Skilled data administrator needs to be hired to manage the complex process.

What is Data Collection Frequency?
Data collection frequency is the rate at which data is collected. However, the data is not just collected and stored. it goes through various stages of processing like extracting from various sources, cleansing, transforming and then storing in useful patterns.
It is important to have a record of the rate at which data is collected because of various reasons:
Companies can use these records to keep a track of the transactions that have occurred. Based on these records the company can know if any invalid transactions ever occurred.
In scenarios where the market changes rapidly, companies need very frequently updated data to enable them make decisions based on the state of the market and then invest appropriately.
A few companies keep launching new products and keep updating their records so that their customers can see them which would in turn increase their business.
When data warehouses face technical problems, the logs as well as the data collection frequency can be used to determine the time and cause of the problem.
Due to real time data collection, database managers and data warehouse specialists can make more room for recording data collection frequency.

What is Data Cardinality?
Cardinality is the term used in database relations to denote the occurrences of data on either side of the relation.
There are 3 basic types of cardinality:
High data cardinality:
Values of a data column are very uncommon.
e.g.: email ids and the user names
Normal data cardinality:
Values of a data column are somewhat uncommon but never unique.
e.g.: A data column containing LAST_NAME (there may be several entries of the same last name)
Low data cardinality:
Values of a data column are very usual.
e.g.: flag statuses: 0/1
Determining data cardinality is a substantial aspect used in data modeling. This is used to determine the relationships
Types of cardinalities:
The Link Cardinality - 0:0 relationships
The Sub-type Cardinality - 1:0 relationships
The Physical Segment Cardinality - 1:1 relationship
The Possession Cardinality - 0: M relation
The Child Cardinality - 1: M mandatory relationship
The Characteristic Cardinality - 0: M relationship
The Paradox Cardinality - 1: M relationship.

What is Chained Data Replication?
In Chain Data Replication, the non-official data set distributed among many disks provides for load balancing among the servers within the data warehouse.
Blocks of data are spread across clusters and each cluster can contain a complete set of replicated data. Every data block in every cluster is a unique permutation of the data in other clusters.
When a disk fails then all the calls made to the data in that disk are redirected to the other disks when the data has been replicated.
At times replicas and disks are added online without having to move around the data in the existing copy or affect the arm movement of the disk.
In load balancing, Chain Data Replication has multiple servers within the data warehouse share data request processing since data already have replicas in each server disk.

What are Critical Success Factors?
Key areas of activity in which favorable results are necessary for a company to reach its goal.
There are four basic types of CSFs which are:
Industry CSFs
Strategy CSFs
Environmental CSFs
Temporal CSFs
A few CSFs are:
Money
Your future
Customer satisfaction
Quality
Product or service development
Intellectual capital
Strategic relationships
Employee attraction and retention
Sustainability
The advantages of identifying CSFs are:
they are simple to understand;
they help focus attention on major concerns;
they are easy to communicate to coworkers;
they are easy to monitor;
and they can be used in concert with strategic planning methodologies.
What is Data Warehousing?
A data warehouse can be considered as a storage area where interest specific or relevant data is stored irrespective of the source. What actually is required to create a data warehouse can be considered as Data Warehousing. Data warehousing merges data from multiple sources into an easy and complete form.

What is Virtual Data Warehousing?
A virtual data warehouse provides a collective view of the completed data. A virtual data warehouse has no historic data. It can be considered as a logical data model of the containing metadata.
Explain in brief various fundamental stages of Data Warehousing.
Stages of a data warehouse helps to find and understand how the data in the warehouse changes.
At an initial stage of data warehousing data of the transactions is merely copied to another server. Here, even if the copied data is processed for reporting, the source data’s performance won’t be affected.
In the next evolving stage, the data in the warehouse is updated regularly using the source data.
In Real time Data warehouse stage data in the warehouse is updated for every transaction performed on the source data (E.g. booking a ticket)
When the warehouse is at integrated stage, It not only updates data as and when a transaction is performed but also generates transactions which are passed back to the source online data.

What is active data warehousing?
An active data warehouse represents a single state of the business. Active data warehousing considers the analytic perspectives of customers and suppliers. It helps to deliver the updated data through reports.

What is data modeling and data mining? What is this used for?
Data Modeling is a technique used to define and analyze the requirements of data that supports organization’s business process. In simple terms, it is used for the analysis of data objects in order to identify the relationships among these data objects in any business.
Data Mining is a technique used to analyze datasets to derive useful insights/information. It is mainly used in retail, consumer goods, telecommunication and financial organizations that have a strong consumer orientation in order to determine the impact on sales, customer satisfaction and profitability. Data Mining is very helpful in determining the relationships among different business attributes.

Difference between ER Modeling and Dimensional Modeling
The entity-relationship model is a method used to represent the logical flow of entities/objects graphically that in turn create a database. It has both logical and physical model. And it is good for reporting and point queries.
Dimensional model is a method in which the data is stored in two types of tables namely facts table and dimension table. It has only physical model. It is good for ad hoc query analysis.

What is the difference between data warehousing and business intelligence?
Data warehousing relates to all aspects of data management starting from the development, implementation and operation of the data sets. It is a back up of all data relevant to business context i.e. a way of storing data
Business Intelligence is used to analyze the data from the point of business to measure any organization’s success. The factors like sales, profitability, marketing campaign effectiveness, market share and operational efficiency etc are analyzed using Business Intelligence tools like Cognos, Informatica, SAS etc.
Describe dimensional Modeling.
Dimensional model is a method in which the data is stored in two types of tables namely facts table and dimension table. Fact table comprises of information to measure business successes and the dimension table comprises of information on which the business success is calculated. It is mainly used by data warehouse designers to build data warehouses. It represents the data in a standard and sequential manner that triggers for high performance access.

What is snapshot with reference to data warehouse?
Snapshot refers to a complete visualization of data at the time of extraction. It occupies less space and can be used to back up and restore data quickly.

J2ME

2009-05-23T20:39:00.000-07:00

Mba Business Schools
The day has finally arrived when you are ready to move out of school and enter college and you have decided to go in for a business school.

SET 1

Q: What is J2ME
A:
Java 2, Micro Edition is a group of specifications and technologies that pertain to Java on small devices. The J2ME moniker covers a wide range of devices, from pagers and mobile telephones through set-top boxes and car navigation systems. The J2ME world is divided into configurations and profiles, specifications that describe a Java environment for a specific class of device.

Q: What is J2ME WTK
A:
The J2ME Wireless Toolkit is a set of tools that provides developers with an emulation environment, documentation and examples for developing Java applications for small devices. The J2ME WTK is based on the Connected Limited Device Configuration (CLDC) and Mobile Information Device Profile (MIDP) reference implementations, and can be tightly integrated with Forte for Java.

Q: What is 802.11
A:
802.11 is a group of specifications for wireless networks developed by the Institute of Electrical and Electronics Engineers (IEEE). 802.11 uses the Ethernet
protocol and CSMA/CA (carrier sense multiple access with collision avoidance) for path sharing.

Q: What is API
A:
An Application Programming Interface (API) is a set of classes that you can use in your own application. Sometimes called libraries or modules, APIs enable you to
write an application without reinventing common pieces of code. For example, a networking API is something your application can use to make network connections, without your ever having to understand the underlying code.

Q: What is AMPS
A:
Advanced Mobile Phone Service (AMPS) is a first-generation analog, circuit-switched cellular phone network. Originally operating in the 800 MHz band, service was later
expanded to include transmissions in the 1900 MHz band, the VHF range in which most wireless carriers operate. Because AMPS uses analog signals, it cannot transmit digital signals and cannot transport data packets without assistance from newer technologies such as TDMA and CDMA.

Q: What is CDC
A:
The Connected Device Configuration (CDC) is a specification for a J2ME configuration. Conceptually, CDC deals with devices with more memory and processing
power than CLDC; it is for devices with an always-on network connection and a minimum of 2 MB of memory available for the Java system.

Q:What is configuration
A:
In J2ME, a configuration defines the minimum Java runtime environment for a family of devices: the combination of a Java virtual machine (either the standard J2SE virtual machine or a much more limited version called the CLDC VM) and a core
set of APIs. CDC and CLDC are configurations. See also profile, optional package.

Q: What is CVM
A:
The Compact Virtual Machine (CVM) is an optimized Java virtual machine1 (JVM) that is used by the CDC.

Q: What is Deck
A:
A deck is a collection of one or more WML cards that can be downloaded, to a mobile phone, as a single entity.

Q: What is EDGE
A:
Enhanced Data GSM Environment (EDGE) is a new, faster version of GSM. EDGE is designed to support transfer rates up to 384Kbps and enable the delivery of video and other high-bandwidth applications. EDGE is the result of a joint effort between TDMA operators, vendors and carriers and the GSM Alliance.

Q: What is ETSI
A:
The European Telecommunications Standards Institute (ETSI) is a non-profit organization that establishes telecommunications standards for Europe.

Q: What is FDMA
A:
Frequency-division multiple-access (FDMA) is a mechanism for sharing a radio frequency band among multiple users by dividing it into a number of smaller bands.

Q: What is Foundation Profile
A:
The Foundation Profile is a J2ME profile specification that builds on CDC. It adds additional classes and interfaces to the CDC APIs but does not go so far as to specify user interface APIs, persistent storage, or application life cycle. Other J2ME profiles build on the CDC/Foundation combination: for example, the Personal Profile and the RMI Profile both build on the Foundation Profile.

Q: What is Generic Connection Framework
A:
The Generic Connection Framework (GCF) makes it easy for wireless devices to make network connections. It is part of CLDC and CDC and resides in the javax.microedition.io package.

Q: What is GPRS
A:
The General Packet Radio System (GPRS) is the next generation of GSM. It will be the basis of 3G networks in Europe and elsewhere.

Q: What is GSM
A:
The Global System for Mobile Communications (GSM) is a wireless network system that is widely used in Europe, Asia, and Australia. GSM is used at three different
frequencies: GSM900 and GSM1800 are used in Europe, Asia, and Australia, while GSM1900 is deployed in North America and other parts of the world.

Q: What is HLR
A:
The Home Location Register (HLR) is a database for permanent storage of subscriber data and service profiles.

Q: What is i-appli
A:
Sometimes called "Java for i-mode", i-appli is a Java environment based on CLDC. It is used on handsets in NTT DoCoMo's i-mode service. While i-appli is similar to
MIDP, it was developed before the MIDP specification was finished and the two APIs are incompatible.

Q: What is iDEN
A:
The Integrated Dispatch Enhanced Network(iDEN) is a wireless network system developed by Motorola. Various carriers support iDEN networks around the world: Nextel is one of the largest carriers, with networks covering North and South America.

Q: What is i-mode
A:
A standard used by Japanese wireless devices to access cHTML (compact HTML) Web sites and display animated GIFs and other multimedia content.

Q: What is 3G
A:
Third generation (3G) wireless networks will offer faster data transfer rates than current networks. The first generation of wireless (1G) was analog cellular. The second generation (2G) is digital cellular, featuring integrated voice and data communications. So-called 2.5G networks offer incremental speed increases. 3G networks will offer dramatically improved data transfer rates, enabling new wireless applications such as streaming media.

Q: What is 3GPP
A:
The 3rd Generation Partnership Project (3GPP) is a global collaboration between 6 partners: ARIB, CWTS, ETSI, T1, TTA, and TTC. The group aims to develop a globally
accepted 3rd-generation mobile system based on GSM

Q: What is Java Card
A:
The Java Card specification allows Java technology to run on smart cards and other small devices. The Java Card API is compatible with formal international standards,
such as, ISO7816, and industry-specific standards, such as, Europay/Master Card/Visa (EMV).

Q: What is JCP
A:
The Java Community Process (JCP) an open organization of international Java developers and licensees who develop and revise Java technology specifications, reference implementations, and technology compatibility kits through a formal
process.

Q: What is JDBC for CDC/FP
A:
The JDBC Optional Package for CDC/Foundation Profile (JDBCOP for CDC/FP) is an API that enables mobile Java applications to communicate with relational database servers using a subset of J2SE's Java Database Connectivity. This optional package is a strict subset of JDBC 3.0 that excludes some of JDBC's advanced and server-oriented features, such as pooled connections and array types. It's meant for use with the Foundation Profile or its supersets.

Q: What is JavaHQ
A:
JavaHQ is the Java platform control center on your Palm OS device.

Q: What is JSR
A:
Java Specification Request (JSR) is the actual description of proposed and final specifications for the Java platform. JSRs are reviewed by the JCP and the public before a final release of a specification is made.

Q: What is KittyHawk
A:
KittyHawk is a set of APIs used by LG Telecom on its IBook and p520 devices. KittyHawk is based on CLDC. It is conceptually similar to MIDP but the two APIs are
incompatible.

Q: What is KJava
A:
KJava is an outdated term for J2ME. It comes from an early package of Java software for PalmOS, released at the 2000 JavaOne show. The classes for that release were
packaged in the com.sun.kjava package.

Q: What is kSOAP
A:
kSOAP is a SOAP API suitable for the J2ME, based on kXML.

Q: What is kXML
A:
The kXML project provides a small footprint XML parser that can be used with J2ME.

Q: What is KVM
A:
The KVM is a compact Java virtual machine (JVM) that is designed for small devices. It supports a subset of the features of the JVM. For example, the KVM does not
support floating-point operations and object finalization. The CLDC specifies use of the KVM. According to folklore, the 'K' in KVM stands for kilobyte, signifying that the KVM runs in kilobytes of memory as opposed to megabytes.

Q: What is LAN
A:
A Local Area Network (LAN) is a group of devices connected with various communications technologies in a small geographic area. Ethernet is the most widely-used LAN technology. Communication on a LAN can either be with Peer-to-Peer
devices or Client-Server devices.

Q: What is LCDUI
A:
LCDUI is a shorthand way of referring to the MIDP user interface APIs, contained in the javax.microedition.lcdui package. Strictly speaking, LCDUI stands for Liquid Crystal Display User Interface. It's a user interface toolkit for small device screens which are commonly LCD screens.

Q: What is MExE
A:
The Mobile Execution Environment(MExE) is a specification created by the 3GPP which details an applicatio n environment for next generation mobile devices. MExE
consists of a variety of technologies including WAP, J2ME, CLDC andMIDP.

Q: What is MIDlet
A:
A MIDlet is an application written for MIDP. MIDlet applications are subclasses of the javax.microedition.midlet.MIDlet class that is defined by MIDP.

Q: What is MIDlet suite
A:
MIDlets are packaged and distributed as MIDlet suites. A MIDlet suite can contain one or more MIDlets. The MIDlet suite consists of two files, an application descriptor file with a .jad extension and an archive file with a .jar file. The descriptor lists the archive file name, the names and class names for each MIDlet in the suite, and other information. The archive file contains the MIDlet classes and resource files.

Q: What is MIDP
A:
The Mobile Information Device Profile (MIDP) is a specification for a J2ME profile. It is layered on top of CLDC and adds APIs for application life cycle, user interface, networking, and persistent storage.

Q: What is MIDP-NG
A:
The Next Generation MIDP specification is currently under development by the Java Community Process. Planned improvements include XML parsing and cryptographic support.

Q: What is Mobitex
A:
Mobitex is a packet-switched, narrowband PCS network, designed for wide-area wireless data communications. It was developed in 1984 by Eritel, an Ericsson
subsidiary, a nd there are now over 30 Mobitex networks in operation worldwide.

Q: What is MSC
A:
A Mobile Switching Center (MSC) is a unit within a cellular phone network that automatically coordinates and switches calls in a given cell. It monitors each
caller's signal strength, and when a signal begins to fade, it hands off the call to another MSC that's better positioned to manage the call.

Q: What is Obfuscation
A:
Obfuscation is a technique used to complicate code. Obfuscation makes code harder to understand when it is de-compiled, but it typically has no affect on the functionality of the code. Obfuscation programs can be used to protect Java programs by making them harder to reverse-engineer.

Q: What is optional package
A:
An optional package is a set of J2ME APIs providing services in a specific area, such as database access or multimedia. Unlike a profile, it does not define a complete application environment, but rather is used in conjunction with a configuration or a profile. It extends the runtime environment to support device capabilities that are not universal enough to be defined as part of a profile or that need to be shared by different profiles. J2ME RMI and the Mobile Media RMI are examples of optional packages.

Q: What is Modulation
A:
Modulation is the method by which a high-frequency digital signal is grafted onto a lower-frequency analog wave, so that digital packets are able to ride piggyback on the analog airwave.

Q: What is OTA
A:
Over The Air (OTA) refers to any wireless networking technology.

Q: What is PCS
A:
Personal Communications Service (PCS) is a suite of second-generation, digitally modulated mobile-communications interfaces that includes TDMA, CDMA, and GSM. PCS
serves as an umbrella term for second-generation wireless technologies operating in the 1900MHz range.

Q: What is PDAP
A:
The Personal Digital Assistant Profile (PDAP) is a J2ME profile specification designed for small platforms such as PalmOS devices. You can think of PDAs as being larger than mobile phones but smaller than set-top boxes. PDAP is built on top of CLDC and will specify user interface and persistent storage APIs. PDAP is currently being developed using the Java Community Process (JCP).

Q: What is PDC
A:
Personal Digital Cellular (PDC) is a Japanese standard for wireless communications.

Q: What is PDCP
A:
Parallel and Distributed Computing Practices (PDCP) are often used to describe computer systems that are spread over many devices on a network (wired or wireless)
where many nodes process data simultaneously.

Q: What is Personal Profile
A:
The Personal Profile is a J2ME profile specification. Layered on the Foundation Profile and CDC, the Personal Profile will be the next generation of PersonalJava
technology. The specification is currently in development under the Java Community Process (JCP).

Q: What is PersonalJava
A:
PersonalJava is a Java environment based on the Java virtual machine1 (JVM) and a set of APIs similar to a JDK 1.1 environment. It includes the Touchable Look and Feel (also called Truffle), a graphic toolkit that is optimized for consumer devices with a touch sensitive screen. PersonalJava will be included in J2ME in the upcoming Personal Profile, which is built on CDC.

Q: What is PNG
A:
Portable Network Graphics (PNG) is an image format offering lossless compression and storage flexibility. The MIDP specification requires implementations to recognize certain types of PNG images.

Q: What is POSE
A:
Palm OS Emulator (POSE).

Q: What is PRC
A:
Palm Resource Code (PRC) is the file format for Palm OS applications.

Q: What is preverification
A:
Due to memory and processing power available on a device, the verification process of classes are split into two processes. The first process is the preverification
which is off-device and done using the preverify tool. The second process is verification which is done on-device.

Q: What is profile
A:
A profile is a set of APIs added to a configuration to support specific uses of a mobile device. Along with its underlying configuration, a profile defines a complete, and usually self-contained, general-purpose application environment.
Profiles often, but not always, define APIs for user interface and persistence; the MIDP profile, based on the CLDC configuration, fits this pattern. Profiles may be supersets or subsets of other profiles; the Personal Basis Profile is a subset of the Personal Profile and a superset of the Foundation Profile. See also configuration, optional package.

Q: What is Provisioning
A:
In telecommunications terms, provisioning means to provide telecommunications services to a user. This includes providing all necessary hardware, software, and wiring or transmission devices.

Q: What is PSTN
A:
The public service telephone network (PSTN) is the traditional, land-line based system for exchanging phone calls.

Q: What is RMI
A:
Remote method invocation (RMI) is a feature of J2SE that enables Java objects running in one virtual machine to invoke methods of Java objects running in another virtual machine, seamlessly.

Q: What is RMI OP
A:
The RMI Optional Package (RMI OP) is a subset of J2SE 1.3's RMI functionality used in CDC-based profiles that incorporate the Foundation Profile, such as the Personal
Basis Profile and the Personal Profile. The RMIOP cannot be used with CLDC-based profiles because they lack object serialization and other important features found only in CDC-based profiles. RMIOP supports most of the J2SE RMI functionality, including the Java Remote Method Protocol, marshalled objects, distributed garbage collection, registry-based object lookup, and network class loading, but not HTTP
tunneling or the Java 1.1 stub protocol.

Q: What is RMI Profile
A:
The RMI Profile is a J2ME profile specification designed to support Java's Remote Method Invocation (RMI) distributed object system. Devices implementing the RMI Profile will be able to interoperate via RMI with other Java devices, including Java 2, Standard Edition. The RMI Profile is based on the Foundation Profile, which in turn is based on CDC.

Q: What is RMS
A:
The Record Management System (RMS) is a simple record-oriented database that allows a MIDlet to persistently store information and retrieve it later. Different MIDlets
can also use the RMS to share data.

Q: What is SIM
A:
A Subscriber Identity Module (SIM) is a stripped-down smart card containing information about the identity of a cell-phone subscriber, and subscriber authentication and service information. Because the SIM uniquely identifies the subscriber and is portable among handsets, the user can move it from one kind of
phone to another, facilitating international roaming.

Q: What is T9
A:
T9 is a text input method for mobile phones and other small devices. It replaces the "multi-tap" input method by guessing the word that you are trying to enter. T9 may be embedded in a device by the manufacturer. Note that even if the device supports T9, the Java implementation may or may not use it. Check your documentation for details.

Q: What is TDMA
A:
Time Division Multiple Access (TDMA) is a second-generation modulation standard using bandwidth allocated in the 800 MHz, 900 MHz, and 1900MHz ranges.

Q: What is W-CDMA
A:
Wideband Code-Division Multiple Access (W-CDMA), also known as IMT-2000, is a 3rd generation wireless technology. Supports speeds up to 384Kbps on a wide-area network, or 2Mbps locally.

Q: What is WDP
A:
Wireless Datagram Protocol (WDP) works as the transport layer of WAP. WDP processes datagrams from upper layers to formats required by different physical datapaths, bearers, that may be for example GSM SMS or CDMA Packet Data. WDP is adapted to
the bearers available in the device so upper layers don't need to care about the physical level.

Q: What is WMA
A:
The Wireless Messaging API (WMA) is a set of classes for sending and receiving Short Message Service messages. See also SMS.

Q: What is WML
A:
The Wireless Markup Language (WML) is a simple language used to create applications for small wireless devices like mobile phones. WML is analogous to HTML in the World Wide Web.

Q: What is WMLScript
A:
WMLScript is a subset of the JavaScript scripting language designed as part of the WAP standard to provide a convenient mechanism to access mobile phone's peripheral
functions.

Q: What is WSP
A:
Wireless Session Protocol (WSP) implements session services of WAP. Sessions can be connection-oriented and connectionless and they may be suspended and resumed at will.

Q: What is WTLS
A:
Wireless Transport Layer Security protocal (WTLS) does all cryptography oriented features of WAP. WTLS handles encryption/decryption, user authentication and data
integrity. WTLS is based on the fixed network Transport Layer Security protocal (TLS), formerly known as Secure Sockets Layer (SSL).

Q: What is WTP
A:
Wireless Transaction Protocol (WTP) is WAP's transaction protocol that works between the session protocol WSP and security protocol WTLS. WTP chops data packets into lower level datagrams and concatenates received datagrams into useful data. WTP also keeps track of received and sent packets and does re-transmissions and acknowledgment sending when needed.

SET 2

1. What is J2ME

Java 2, Micro Edition is a group of specifications and technologies that pertain to Java on small devices. The J2ME moniker covers a wide range of devices, from pagers and mobile telephones through set-top boxes and car navigation systems. The J2ME world is divided into configurations and profiles, specifications that describe a Java environment for a specific class of device.

2. What is J2ME WTK

The J2ME Wireless Toolkit is a set of tools that provides developers with an emulation environment, documentation and examples for developing Java applications for small devices. The J2ME WTK is based on the Connected Limited Device Configuration (CLDC) and Mobile Information Device Profile (MIDP) reference implementations, and can be tightly integrated with Forte for Java

3. What is 802.11

802.11 is a group of specifications for wireless networks developed by the Institute of Electrical and Electronics Engineers (IEEE). 802.11 uses the Ethernet protocol and CSMA/CA (carrier sense multiple access with collision avoidance) for path sharing.

4. What is API

An Application Programming Interface (API) is a set of classes that you can use in your own application. Sometimes called libraries or modules, APIs enable you to write an application without reinventing common pieces of code. For example, a networking API is something your application can use to make network connections, without your ever having to understand the underlying code.

5. What is AMPS

Advanced Mobile Phone Service (AMPS) is a first-generation analog, circuit-switched cellular phone network. Originally operating in the 800 MHz band, service was later expanded to include transmissions in the 1900 MHz band, the VHF range in which most wireless carriers operate. Because AMPS uses analog signals, it cannot transmit digital signals and cannot transport data packets without assistance from newer technologies such as TDMA and CDMA.

6. What is CDC

The Connected Device Configuration (CDC) is a specification for a J2ME configuration. Conceptually, CDC deals with devices with more memory and processing power than CLDC; it is for devices with an always-on network connection and a minimum of 2 MB of memory available for the Java system

7. What is CDMA

Code-Division Multiple Access (CDMA) is a cellular technology widely used in North America. There are currently three CDMA standards: CDMA One, CDMA2000 and W-CDMA. CDMA technology uses UHF 800Mhz-1.9Ghz frequencies and bandwidth ranges from 115Kbs to 2Mbps.

8. What is CDMA One

Also know as IS-95, CDMAOne is a 2nd generation wireless technology. Supports speeds from 14.4Kbps to 115K bps.

9. What is CDMA2000

Also known as IS-136, CDMA2000 is a 3rd generation wireless technology. Supports speeds ranging from 144Kbps to 2Mbps.

10. What is CDPD

Developed by Nortel Networks, Cellular Digital Packet Data (CDPD) is an open standard for supporting wireless Internet access from cellular devices. CDPD also supports Multicast, which allows content providers to efficiently broadcast information to many devices at the same time.

11. What is cHTML

Compact HTML (cHTML) is a subset of HTML which is designed for small devices. The major features of HTML that are excluded from cHTML are: JPEG image, Table, Image map, Multiple character fonts and styles, Background color and image, Frame and Style sheet.

12. What is CLDC

The Connected, Limited Device Configuration (CLDC) is a specification for a J2ME configuration. The CLDC is for devices with less than 512 KB or RAM available for the Java system and an intermittent (limited) network connection. It specifies a stripped-down Java virtual machine1 called the KVM as well as several APIs for fundamental application services. Three packages are minimalist versions of the J2SE java.lang, java.io, and java.util packages. A fourth package, javax.microedition.io, implements the Generic Connection Framework, a generalized API for making network connection

13. What is configuration

In J2ME, a configuration defines the minimum Java runtime environment for a family of devices: the combination of a Java virtual machine (either the standard J2SE virtual machine or a much more limited version called the CLDC VM) and a core set of APIs. CDC and CLDC are configurations. See also profile, optional package.

14. What is CVM

The Compact Virtual Machine (CVM) is an optimized Java virtual machine1 (JVM) that is used by the CDC.

15. What is Deck

A deck is a collection of one or more WML cards that can be downloaded, to a mobile phone, as a single entity.

16. What is EDGE

Enhanced Data GSM Environment (EDGE) is a new, faster version of GSM. EDGE is designed to support transfer rates up to 384Kbps and enable the delivery of video and other high-bandwidth applications. EDGE is the result of a joint effort between TDMA operators, vendors and carriers and the GSM Alliance.

17. What is ETSI

The European Telecommunications Standards Institute (ETSI) is a non-profit organization that establishes telecommunications standards for Europe.

18. What is FDMA

Frequency-division multiple-access (FDMA) is a mechanism for sharing a radio frequency band among multiple users by dividing it into a number of smaller bands.

19. What is Foundation Profile

The Foundation Profile is a J2ME profile specification that builds on CDC. It adds additional classes and interfaces to the CDC APIs but does not go so far as to specify user interface APIs, persistent storage, or application life cycle. Other J2ME profiles build on the CDC/Foundation combination: for example, the Personal Profile and the RMI Profile both build on the Foundation Profile.

20. What is Generic Connection Framework

The Generic Connection Framework (GCF) makes it easy for wireless devices to make network connections. It is part of CLDC and CDC and resides in the javax.microedition.io package.

21. What is GPRS

The General Packet Radio System (GPRS) is the next generation of GSM. It will be the basis of 3G networks in Europe and elsewhere.

22. What is GSM

The Global System for Mobile Communications (GSM) is a wireless network system that is widely used in Europe, Asia, and Australia. GSM is used at three different frequencies: GSM900 and GSM1800 are used in Europe, Asia, and Australia, while GSM1900 is deployed in North America and other parts of the world.

23. What is HLR

The Home Location Register (HLR) is a database for permanent storage of subscriber data and service profiles.

24. What is HTTPS

Hyper Text Transfer Protocol Secure sockets (HTTPS) is a protocol for transmission of encrypted hypertext over Secure Sockets Layer

25. What is i-appli

Sometimes called "Java for i-mode", i-appli is a Java environment based on CLDC. It is used on handsets in NTT DoCoMo's i-mode service. While i-appli is similar to MIDP, it was developed before the MIDP specification was finished and the two APIs are incompatible.

26. What is IDE

An Integrated Development Environment (IDE) provides a programming environment as a single application. IDEs typically bundle a compiler, debugger, and GUI builder tog ether. Forte for Java is Sun's Java IDE.

27. What is iDEN

The Integrated Dispatch Enhanced Network (iDEN) is a wireless network system developed by Motorola. Various carriers support iDEN networks around the world: Nextel is one of the largest carriers, with networks covering North and South America.

28. What is i-mode

A standard used by Japanese wireless devices to access cHTML (compact HTML) Web sites and display animated GIFs and other multimedia content.

29. What is 3G

Third generation (3G) wireless networks will offer faster data transfer rates than current networks. The first generation of wireless (1G) was analog cellular. The second generation (2G) is digital cellular, featuring integrated voice and data communications. So-called 2.5G networks offer incremental speed increases. 3G networks will offer dramatically improved data transfer rates, enabling new wireless applications such as streaming media.

30. What is 3GPP

The 3rd Generation Partnership Project (3GPP) is a global collaboration between 6 partners: ARIB, CWTS, ETSI, T1, TTA, and TTC. The group aims to develop a globally accepted 3rd-generation mobile system based on GSM.

31. What is Java Card

The Java Card specification allows Java technology to run on smart cards and other small devices. The Java Card API is compatible with formal international standards, such as, ISO7816, and industry-specific standards, such as, Europay/Master Card/Visa (EMV).

32. What is JavaHQ

JavaHQ is the Java platform control center on your Palm OS device.

33. What is JCP

The Java Community Process (JCP) an open organization of international Java developers and licensees who develop and revise Java technology specifications, reference implementations, and technology compatibility kits through a formal process.

34. What is JDBC for CDC/FP

The JDBC Optional Package for CDC/Foundation Profile (JDBCOP for CDC/FP) is an API that enables mobile Java applications to communicate with relational database servers using a subset of J2SE's Java Database Connectivity. This optional package is a strict subset of JDBC 3.0 that excludes some of JDBC's advanced and server-oriented features, such as pooled connections and array types. It's meant for use with the Foundation Profile or its supersets.

35. What is JSR

Java Specification Request (JSR) is the actual description of proposed and final specifications for the Java platform. JSRs are reviewed by the JCP and the public before a final release of a specification is made.

36. What is KittyHawk

KittyHawk is a set of APIs used by LG Telecom on its IBook and p520 devices. KittyHawk is based on CLDC. It is conceptually similar to MIDP but the two APIs are incompatible.

37. What is KJava

KJava is an outdated term for J2ME. It comes from an early package of Java software for PalmOS, released at the 2000 JavaOne show. The classes for that release were packaged in the com.sun.kjava package.

38. What is kSOAP

kSOAP is a SOAP API suitable for the J2ME, based on kXML.

39. What is kXML

The kXML project provides a small footprint XML parser that can be used with J2ME.

40. What is KVM

The KVM is a compact Java virtual machine (JVM) that is designed for small devices. It supports a subset of the features of the JVM. For example, the KVM does not support floating-point operations and object finalization. The CLDC specifies use of the KVM. According to folklore, the 'K' in KVM stands for kilobyte, signifying that the KVM runs in kilobytes of memory as opposed to megabytes.

41. What is LAN

A Local Area Network (LAN) is a group of devices connected with various communications technologies in a small geographic area. Ethernet is the most widely-used LAN technology. Communication on a LAN can either be with Peer-to-Peer devices or Client-Server devices.

42. What is LCDUI

LCDUI is a shorthand way of referring to the MIDP user interface APIs, contained in the javax.microedition.lcdui package. Strictly speaking, LCDUI stands for Liquid Crystal Display User Interface. It's a user interface toolkit for small device screens which are commonly LCD screens

43. What is MExE

The Mobile Execution Environment (MExE) is a specification created by the 3GPP which details an applicatio n environment for next generation mobile devices. MExE consists of a variety of technologies including WAP, J2ME, CLDC and MIDP.

44. What is MIDlet

A MIDlet is an application written for MIDP. MIDlet applications are subclasses of the javax.microedition.midlet.MIDlet class that is defined by MIDP.

45. What is MIDlet suite

MIDlets are packaged and distributed as MIDlet suites. A MIDlet suite can contain one or more MIDlets. The MIDlet suite consists of two files, an application descriptor file with a .jad extension and an archive file with a .jar file. The descriptor lists the archive file name, the names and class names for each MIDlet in the suite, and other information. The archive file contains the MIDlet classes and resource files.

46. What is MIDP

The Mobile Information Device Profile (MIDP) is a specification for a J2ME profile. It is layered on top of CLDC and adds APIs for application life cycle, user interface, networking, and persistent storage.

47. What is MIDP-NG

The Next Generation MIDP specification is currently under development by the Java Community Process. Planned improvements include XML parsing and cryptographic support.

48. What is Mobitex

Mobitex is a packet-switched, narrowband PCS network, designed for wide-area wireless data communications. It was developed in 1984 by Eritel, an Ericsson subsidiary, a nd there are now over 30 Mobitex networks in operation worldwide.

49. What is Modulation

Modulation is the method by which a high-frequency digital signal is grafted onto a lower-frequency analog wave, so that digital packets are able to ride piggyback on the analog airwave.

50. What is MSC

A Mobile Switching Center (MSC) is a unit within a cellular phone network that automatically coordinates and switches calls in a given cell. It monitors each caller's signal strength, and when a signal begins to fade, it hands off the call to another MSC that's better positioned to manage the call.

51. What is Obfuscation

Obfuscation is a technique used to complicate code. Obfuscation makes code harder to understand when it is de-compiled, but it typically has no affect on the functionality of the code. Obfuscation programs can be used to protect Java programs by making them harder to reverse-engineer.

52. What is optional package

An optional package is a set of J2ME APIs providing services in a specific area, such as database access or multimedia. Unlike a profile, it does not define a complete application environment, but rather is used in conjunction with a configuration or a profile. It extends the runtime environment to support device capabilities that are not universal enough to be defined as part of a profile or that need to be shared by different profiles. J2ME RMI and the Mobile Media RMI are examples of optional packages.

53. What is OTA

Over The Air (OTA) refers to any wireless networking technology.

54. What is PCS

Personal Communications Service (PCS) is a suite of second-generation, digitally modulated mobile-communications interfaces that includes TDMA, CDMA, and GSM. PCS serves as an umbrella term for second-generation wireless technologies operating in the 1900MHz range

55. What is PDAP

The Personal Digital Assistant Profile (PDAP) is a J2ME profile specification designed for small platforms such as PalmOS devices. You can think of PDAs as being larger than mobile phones but smaller than set-top boxes. PDAP is built on top of CLDC and will specify user interface and persistent storage APIs. PDAP is currently being developed using the Java Community Process (JCP).

56. What is PDC

Personal Digital Cellular (PDC) is a Japanese standard for wireless communications.

57. What is PDCP

Parallel and Distributed Computing Practices (PDCP) are often used to describe computer systems that are spread over many devices on a network (wired or wireless) where many nodes process data simultaneously.

58. What is Personal Profile

The Personal Profile is a J2ME profile specification. Layered on the Foundation Profile and CDC, the Personal Profile will be the next generation of PersonalJava technology. The specification is currently in development under the Java Community Process (JCP).

59. What is PersonalJava

PersonalJava is a Java environment based on the Java virtual machine1 (JVM) and a set of APIs similar to a JDK 1.1 environment. It includes the Touchable Look and Feel (also called Truffle), a graphic toolkit that is optimized for consumer devices with a touch sensitive screen. PersonalJava will be included in J2ME in the upcoming Personal Profile, which is built on CDC.

60. What is PNG

Portable Network Graphics (PNG) is an image format offering lossless compression and storage flexibility. The MIDP specification requires implementations to recognize certain types of PNG images.

61. What is POSE

Palm OS Emulator (POSE).

62. What is PRC

Palm Resource Code (PRC) is the file format for Palm OS applications.

63. What is preverification

Due to memory and processing power available on a device, the verification process of classes are split into two processes. The first process is the preverification which is off-device and done using the preverify tool. The second process is verification which is done on-device.

64. What is profile

A profile is a set of APIs added to a configuration to support specific uses of a mobile device. Along with its underlying configuration, a profile defines a complete, and usually self-contained, general-purpose application environment. Profiles often, but not always, define APIs for user interface and persistence; the MIDP profile, based on the CLDC configuration, fits this pattern. Profiles may be supersets or subsets of other profiles; the Personal Basis Profile is a subset of the Personal Profile and a superset of the Foundation Profile. See also configuration, optional package.

65. What is Provisioning

In telecommunications terms, provisioning means to provide telecommunications services to a user. This includes providing all necessary hardware, software, and wiring or transmission devices.

67. What is PSTN

The public service telephone network (PSTN) is the traditional, land-line based system for exchanging phone calls.

68. What is RMI

Remote method invocation (RMI) is a feature of J2SE that enables Java objects running in one virtual machine to invoke methods of Java objects running in another virtual machine, seamlessly.

69. What is RMI OP

The RMI Optional Package (RMI OP) is a subset of J2SE 1.3's RMI functionality used in CDC-based profiles that incorporate the Foundation Profile, such as the Personal Basis Profile and the Personal Profile. The RMIOP cannot be used with CLDC-based profiles because they lack object serialization and other important features found only in CDC-based profiles. RMIOP supports most of the J2SE RMI functionality, including the Java Remote Method Protocol, marshalled objects, distributed garbage collection, registry-based object lookup, and network class loading, but not HTTP tunneling or the Java 1.1 stub protocol.

70. What is RMI Profile

The RMI Profile is a J2ME profile specification designed to support Java's Remote Method Invocation (RMI) distributed object system. Devices implementing the RMI Profile will be able to interoperate via RMI with other Java devices, including Java 2, Standard Edition. The RMI Profile is based on the Foundation Profile, which in turn is based on CDC.

71. What is RMS

The Record Management System (RMS) is a simple record-oriented database that allows a MIDlet to persistently store information and retrieve it later. Different MIDlets can also use the RMS to share data.

72. What is SDK

A Software Development Kit (SDK) is a set of tools used to develop applications for a particular platform. An SDK typically contains a compiler, linker, and debugger. It may also contain libraries and documentation for APIs.

73. What is SIM

A Subscriber Identity Module (SIM) is a stripped-down smart card containing information about the identity of a cell-phone subscriber, and subscriber authentication and service information. Because the SIM uniquely identifies the subscriber and is portable among handsets, the user can move it from one kind of phone to another, facilitating international roaming.

74. What is SMS

Short Message Service (SMS) is a point-to-point service similar to paging for sending text messages of up to 160 characters to mobile phones.

75. What is SOAP

The Simple Object Access Protocol (SOAP) is an XML- based protocol that allows objects of any type to communicated in a distributed environment. SOAP is used in developing Web Services.

76. What is SSL

Secure Sockets Layer (SSL) is a socket protocol that encrypts data sent over the network and provides authentication for the socket endpoints.

77. What is T9

T9 is a text input method for mobile phones and other small devices. It replaces the "multi-tap" input method by guessing the word that you are trying to enter. T9 may be embedded in a device by the manufacturer. Note that even if the device supports T9, the Java implementation may or may not use it. Check your documentation for details.

78. What is TDMA

Time Division Multiple Access (TDMA) is a second-generation modulation standard using bandwidth allocated in the 800 MHz, 900 MHz, and 1900MHz ranges.

85. What is WAP

Wireless Application Protocol (WAP) is a protocol for transmitting data between servers and clients (usually small wireless devices like mobile phones). WAP is analogous to HTTP in the World Wide Web. Many mobile phones include WAP browser software to allow users access to Internet WAP sites.

86. What is WAP Gateway

A WAP Gateway acts as a bridge allowing WAP devices to communicate with other networks (namely the Internet).

87. What is W-CDMA

Wideband Code-Division Multiple Access (W-CDMA), also known as IMT-2000, is a 3rd generation wireless technology. Supports speeds up to 384Kbps on a wide-area network, or 2Mbps locally.

88. What is WDP

Wireless Datagram Protocol (WDP) works as the transport layer of WAP. WDP processes datagrams from upper layers to formats required by different physical datapaths, bearers, that may be for example GSM SMS or CDMA Packet Data. WDP is adapted to the bearers available in the device so upper layers don't need to care about the physical level.

89. What is WMA

The Wireless Messaging API (WMA) is a set of classes for sending and receiving Short Message Service messages. See also SMS.

90. What is WML

The Wireless Markup Language (WML) is a simple language used to create applications for small wireless devices like mobile phones. WML is analogous to HTML in the World Wide Web

91. What is WMLScript

WMLScript is a subset of the JavaScript scripting language designed as part of the WAP standard to provide a convenient mechanism to access mobile phone's peripheral functions.

92. What is WSP

Wireless Session Protocol (WSP) implements session services of WAP. Sessions can be connection-oriented and connectionless and they may be suspended and resumed at will.

93. What is WTLS

Wireless Transport Layer Security protocal (WTLS) does all cryptography oriented features of WAP. WTLS handles encryption/decryption, user authentication and data integrity. WTLS is based on the fixed network Transport Layer Security protocal (TLS), formerly known as Secure Sockets Layer (SSL).

95. What is WTP

Wireless Transaction Protocol (WTP) is WAP's transaction protocol that works between the session protocol WSP and security protocol WTLS. WTP chops data packets into lower level datagrams and concatenates received datagrams into useful data. WTP also keeps track of received and sent packets and does re-transmissions and acknowledgment sending when needed.

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SQL

2009-05-13T23:23:00.000-07:00

What is normalization? Explain different levels of normalization?

Check out the article Q100139 from Microsoft knowledge base and of
course, there's much more information available in the net. It'll be a
good idea to get a hold of any RDBMS fundamentals text book,
especially the one by C. J. Date. Most of the times, it will be okay
if you can explain till third normal form.

What is denormalization and when would you go for it?

As the name indicates, denormalization is the reverse process of
normalization. It's the controlled introduction of redundancy in to
the database design. It helps improve the query performance as the
number of joins could be reduced.

How do you implement one-to-one, one-to-many and many-to-many
relationships while designing tables?

One-to-One relationship can be implemented as a single table and
rarely as two tables with primary and foreign key relationships.
One-to-Many relationships are implemented by splitting the data into
two tables with primary key and foreign key relationships.
Many-to-Many relationships are implemented using a junction table with
the keys from both the tables forming the composite primary key of the
junction table.

What's the difference between a primary key and a unique key?

Both primary key and unique enforce uniqueness of the column on which
they are defined. But by default primary key creates a clustered index
on the column, where are unique creates a nonclustered index by
default. Another major difference is that, primary key doesn't allow
NULLs, but unique key allows one NULL only.

What are user defined datatypes and when you should go for them?

User defined datatypes let you extend the base SQL Server datatypes by
providing a descriptive name, and format to the database. Take for
example, in your database, there is a column called Flight_Num which
appears in many tables. In all these tables it should be varchar(8).
In this case you could create a user defined datatype called
Flight_num_type of varchar(8) and use it across all your tables.

What is bit datatype and what's the information that can be stored
inside a bit column?

Bit datatype is used to store boolean information like 1 or 0 (true or
false). Untill SQL Server 6.5 bit datatype could hold either a 1 or 0
and there was no support for NULL. But from SQL Server 7.0 onwards,
bit datatype can represent a third state, which is NULL.

Define candidate key, alternate key, composite key.

A candidate key is one that can identify each row of a table uniquely.
Generally a candidate key becomes the primary key of the table. If the
table has more than one candidate key, one of them will become the
primary key, and the rest are called alternate keys.

A key formed by combining at least two or more columns is called
composite key.

What are defaults? Is there a column to which a default can't be bound?

A default is a value that will be used by a column, if no value is
supplied to that column while inserting data. IDENTITY columns and
timestamp columns can't have defaults bound to them.

What is a transaction and what are ACID properties?

A transaction is a logical unit of work in which, all the steps must
be performed or none. ACID stands for Atomicity, Consistency,
Isolation, Durability. These are the properties of a transaction.

Explain different isolation levels

An isolation level determines the degree of isolation of data between
concurrent transactions. The default SQL Server isolation level is
Read Committed. Here are the other isolation levels (in the ascending
order of isolation): Read Uncommitted, Read Committed, Repeatable
Read, Serializable. See SQL Server books online for an explanation of
the isolation levels. Be sure to read about SET TRANSACTION ISOLATION
LEVEL, which lets you customize the isolation level at the connection
level.

CREATE INDEX myIndex ON myTable(myColumn)

What type of Index will get created after executing the above statement?

Non-clustered index. Important thing to note: By default a clustered
index gets created on the primary key, unless specified otherwise.

What's the maximum size of a row?

8060 bytes.

What is lock escalation?

Lock escalation is the process of converting a lot of low level locks
(like row locks, page locks) into higher level locks (like table
locks). Every lock is a memory structure too many locks would mean,
more memory being occupied by locks. To prevent this from happening,
SQL Server escalates the many fine-grain locks to fewer coarse-grain
locks. Lock escalation threshold was definable in SQL Server 6.5, but
from SQL Server 7.0 onwards it's dynamically managed by SQL Server.

What's the difference between DELETE TABLE and TRUNCATE TABLE commands?

DELETE TABLE is a logged operation, so the deletion of each row gets
logged in the transaction log, which makes it slow. TRUNCATE TABLE
also deletes all the rows in a table, but it won't log the deletion of
each row, instead it logs the deallocation of the data pages of the
table, which makes it faster. Of course, TRUNCATE TABLE can be rolled
back.

Explain the storage models of OLAP

Check out MOLAP, ROLAP and HOLAP in SQL Server books online for more
infomation.

What are constraints? Explain different types of constraints.

Constraints enable the RDBMS enforce the integrity of the database
automatically, without needing you to create triggers, rule or defaults.

Types of constraints: NOT NULL, CHECK, UNIQUE, PRIMARY KEY, FOREIGN KEY

What is RAID

RAID stands for Redundant Array of Inexpensive Disks, used to provide
fault tolerance to database servers. There are six RAID levels 0
through 5 offering different levels of performance, fault tolerance.

What is a deadlock and what is a live lock? How will you go about
resolving deadlocks?

Deadlock is a situation when two processes, each having a lock on one
piece of data, attempt to acquire a lock on the other's piece. Each
process would wait indefinitely for the other to release the lock,
unless one of the user processes is terminated. SQL Server detects
deadlocks and terminates one user's process.

A livelock is one, where a request for an exclusive lock is
repeatedly denied because a series of overlapping shared locks keeps
interfering. SQL Server detects the situation after four denials and
refuses further shared locks. A livelock also occurs when read
transactions monopolize a table or page, forcing a write transaction
to wait indefinitely.

What is blocking and how would you troubleshoot it?

Blocking happens when one connection from an application holds a lock
and a second connection requires a conflicting lock type. This forces
the second connection to wait, blocked on the first.

What are the different ways of moving data/databases between servers
and databases in SQL Server?

There are lots of options available, you have to choose your option
depending upon your requirements. Some of the options you have are:
BACKUP/RESTORE, dettaching and attaching databases, replication, DTS,
BCP, logshipping, INSERT...SELECT, SELECT...INTO, creating INSERT
scripts to generate data.

What is database replicaion? What are the different types of
replication you can set up in SQL Server?

Replication is the process of copying/moving data between databases on
the same or different servers. SQL Server supports the following types
of replication scenarios:

* Snapshot replication
* Transactional replication (with immediate updating subscribers,
with queued updating subscribers)
* Merge replication

What are cursors? Explain different types of cursors. What are the
disadvantages of cursors? How can you avoid cursors?

Cursors allow row-by-row prcessing of the resultsets.

Types of cursors: Static, Dynamic, Forward-only, Keyset-driven. See
books online for more information.

Disadvantages of cursors: Each time you fetch a row from the cursor,
it results in a network roundtrip, where as a normal SELECT query
makes only one rowundtrip, however large the resultset is. Cursors are
also costly because they require more resources and temporary storage
(results in more IO operations). Furthere, there are restrictions on
the SELECT statements that can be used with some types of cursors.

Most of the times, set based operations can be used instead of
cursors. Here is an example:

If you have to give a flat hike to your employees using the following
criteria:

Salary between 30000 and 40000 -- 5000 hike
Salary between 40000 and 55000 -- 7000 hike
Salary between 55000 and 65000 -- 9000 hike

In this situation many developers tend to use a cursor, determine each
employee's salary and update his salary according to the above
formula. But the same can be achieved by multiple update statements or
can be combined in a single UPDATE statement as shown below:

UPDATE tbl_emp SET salary =
CASE WHEN salary BETWEEN 30000 AND 40000 THEN salary + 5000
WHEN salary BETWEEN 40000 AND 55000 THEN salary + 7000
WHEN salary BETWEEN 55000 AND 65000 THEN salary + 10000
END

Another situation in which developers tend to use cursors: You need to
call a stored procedure when a column in a particular row meets
certain condition. You don't have to use cursors for this. This can be
achieved using WHILE loop, as long as there is a unique key to
identify each row. For examples of using WHILE loop for row by row
processing, check out the 'My code library' section of my site or
search for WHILE.

What is a join and explain different types of joins.

Joins are used in queries to explain how different tables are related.
Joins also let you select data from a table depending upon data from
another table.

Types of joins: INNER JOINs, OUTER JOINs, CROSS JOINs. OUTER JOINs are
further classified as LEFT OUTER JOINS, RIGHT OUTER JOINS and FULL
OUTER JOINS.

What is a self join? Explain it with an example.

Self join is just like any other join, except that two instances of
the same table will be joined in the query. Here is an example:
Employees table which contains rows for normal employees as well as
managers. So, to find out the managers of all the employees, you need
a self join.

CREATE TABLE emp
(
empid int,
mgrid int,
empname char(10)
)

INSERT emp SELECT 1,2,'Vyas'
INSERT emp SELECT 2,3,'Mohan'
INSERT emp SELECT 3,NULL,'Shobha'
INSERT emp SELECT 4,2,'Shridhar'
INSERT emp SELECT 5,2,'Sourabh'

SELECT t1.empname [Employee], t2.empname [Manager]
FROM emp t1, emp t2
WHERE t1.mgrid = t2.empid

Here's an advanced query using a LEFT OUTER JOIN that even returns the
employees without managers (super bosses)

SELECT t1.empname [Employee], COALESCE(t2.empname, 'No manager') [Manager]
FROM emp t1
LEFT OUTER JOIN
emp t2
ON
t1.mgrid = t2.empid

sql

Explain an outer join?

An outer join includes rows from tables when there are no matching values in the tables.

What is a subselect? Is it different from a nested select?
A subselect is a select which works in conjunction with another select. A nested select is a kind of subselect where the inner select passes to the where criteria for the outer select.

What is the difference between group by and order by?
Group by controls the presentation of the rows, order by controls the presentation of the columns for the results of the SELECT statement.

What keyword does an SQL SELECT statement use for a string search?
The LIKE keyword allows for string searches. The % sign is used as a wildcard.

What are some SQL aggregates and other built-in functions?
The common aggregate, built-in functions are AVG, SUM, MIN, MAX, COUNT and DISTINCT.

How is the SUBSTR keyword used in SQL?
SUBSTR is used for string manipulation with column name, first position and string length used as arguments. E.g. SUBSTR (NAME, 1 3) refers to the first three characters in the column NAME.

Explain the EXPLAIN statement?
The explain statement provides information about the optimizer's choice of access path of the SQL.

What is referential integrity?
Referential integrity refers to the consistency that must be maintained between primary and foreign keys, i.e. every foreign key value must have a corresponding primary key value.

What is a NULL value? What are the pros and cons of using NULLS?
A NULL value takes up one byte of storage and indicates that a value is not present as opposed to a space or zero value. It's the DB2 equivalent of TBD on an organizational chart and often correctly portrays a business situation.Unfortunately, it requires extra coding for an application program to handle this situation.

What is a synonym? How is it used?
A synonym is used to reference a table or view by another name. The other name can then be written in the application code pointing to test tables in the development stage and to production entities when the code is migrated.
The synonym is linked to the AUTHID that created it.

What is an alias and how does it differ from a synonym?
An alias is an alternative to a synonym, designed for a distributed environment to avoid having to use the location qualifier of a table or view. The alias is not dropped when the table is dropped.

When can an insert of a new primary key value threaten referential integrity?
Never. New primary key values are not a problem. However, the values of foreign key inserts must have corresponding primary key values in their related tables. And updates of primary key values may require changes in foreign key values to maintain referential integrity.

What is the difference between static and dynamic SQL?
Static SQL is hard-coded in a program when the programmer knows the statements to be executed. For dynamic SQL the program must dynamically allocate memory to receive the query results.

Compare a subselect to a join?
Any subselect can be rewritten as a join, but not vice versa. Joins are usually more efficient as join rows can be returned immediately, subselects require a temporary work area for inner selects results while processing the outer select.

What is the difference between IN subselects and EXISTS subselect?
If there is an index on the attributes tested an IN is more efficient since DB2 uses the index for the IN. (IN for index is the mnemonic).

What is a Cartesian product?
A Cartesian product results from a faulty query. It is a row in the results for every combination in the join tables.

What is a tuple?
A tuple is an instance of data within a relational database.

What is the difference between static and dynamic SQL?
Static SQL is compiled and optimized prior to its execution; dynamic is compiled and optimized during execution.

What are common SQL abend codes? (e.g. : 0,100 etc.,)

-818 time stamp mismatch

-180 wrong data moved into date field

What is meant by dynamic SQL?

Dynamic SQL are SQL statements that are prepared and executed within a program while the program is executing.

The SQL source is contained in host variables rather than being hard coded into the program. The SQL statement may

change from execution to execution.

What is meant by embedded SQL?

They are SQL statements that are embedded with in application program and are prepared during the program

preparation process before the program is executed. After it is prepared, the statement itself does not change(although

values of host variables specified within the statement might change).

NETWORKING

2009-05-13T22:51:00.000-07:00

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1. What are 10Base2, 10Base5 and 10BaseT Ethernet LANs
10Base2—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband
signaling, with a contiguous cable segment length of 100
meters and a maximum of 2 segments.
10Base5—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband
signaling, with 5 continuous segments not exceeding 100
meters per segment.
10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband
signaling and twisted pair cabling.

2. Explain the difference between an unspecified passive open and a fully specified passive open
An unspecified passive open has the server waiting for a connection request from a client. A fully specified passive
open has the server waiting for a connection from a
specific client.

3. Explain the function of Transmission Control Block
A TCB is a complex data structure that contains a considerable amount of information about each connection.

4. Explain a Management Information Base (MIB)
A Management Information Base is part of every SNMP-managed device. Each SNMP agent has the MIB database that
contains information about the device's status, its
performance, connections, and configuration. The MIB is queried by SNMP.

5. Explain anonymous FTP and why would you use it
Anonymous FTP enables users to connect to a host without using a valid login and password. Usually, anonymous FTP
uses a login called anonymous or guest, with the
password usually requesting the user's ID for tracking purposes only. Anonymous FTP is used to enable a large number
of users to access files on the host without having
to go to the trouble of setting up logins for them all. Anonymous FTP systems usually have strict controls over the areas
an anonymous user can access.

6. Explain a pseudo tty
A pseudo tty or false terminal enables external machines to connect through Telnet or rlogin. Without a pseudo tty, no
connection can take place.

7. Explain REX
What advantage does REX offer other similar utilities

8. What does the Mount protocol do
The Mount protocol returns a file handle and the name of the file system in which a requested file resides. The message
is sent to the client from the server after reception
of a client's request.

9. Explain External Data Representation
External Data Representation is a method of encoding data within an RPC message, used to ensure that the data is not
system-dependent.

10. Explain the Network Time Protocol ?

11. BOOTP helps a diskless workstation boot. How does it get a message to the network looking for its IP address and the location of its operating system boot files
BOOTP sends a UDP message with a subnetwork broadcast address and waits for a reply from a server that gives it the IP address. The same message might contain the name of the machine that has the boot files on it. If the boot image location is not specified, the workstation sends another UDP message to query the server.

12. Explain a DNS resource record
A resource record is an entry in a name server's database. There are several types of resource records used, including name-to-address resolution information. Resource records are maintained as ASCII files.

13. What protocol is used by DNS name servers
DNS uses UDP for communication between servers. It is a better choice than TCP because of the improved speed a connectionless protocol offers. Of course, transmission reliability suffers with UDP.

14. Explain the difference between interior and exterior neighbor gateways
Interior gateways connect LANs of one organization, whereas exterior gateways connect the organization to the outside world.

15. Explain the HELLO protocol used for
The HELLO protocol uses time instead of distance to determine optimal routing. It is an alternative to the Routing Information Protocol.

16. What are the advantages and disadvantages of the three types of routing tables
The three types of routing tables are fixed, dynamic, and fixed central. The fixed table must be manually modified every time there is a change. A dynamic table changes its information based on network traffic, reducing the amount of manual maintenance. A fixed central table lets a manager modify only one table, which is then read by other devices. The fixed central table reduces the need to update each machine's table, as with the fixed table. Usually a dynamic table causes the fewest problems for a network
administrator, although the table's contents can change without the administrator being aware of the change.

17. Explain a TCP connection table

18. Explain source route
It is a sequence of IP addresses identifying the route a datagram must follow. A source route may
optionally be included in an IP datagram header.

19. Explain RIP (Routing Information Protocol)
It is a simple protocol used to exchange information between the routers.

20. Explain SLIP (Serial Line Interface Protocol)
It is a very simple protocol used for transmission of IP datagrams across a serial line.

21. Explain Proxy ARP
It is using a router to answer ARP requests. This will be done when the originating host believes that a destination is local, when in fact is lies beyond router.

22. Explain OSPF
It is an Internet routing protocol that scales well, can route traffic along multiple paths, and uses knowledge of an Internet's topology to make accurate routing decisions.

23. Explain Kerberos
It is an authentication service developed at the Massachusetts Institute of Technology. Kerberos uses encryption to prevent intruders from discovering passwords and gaining unauthorized access to files.

24. Explain a Multi-homed Host
It is a host that has a multiple network interfaces and that requires multiple IP addresses is called as a Multi-homed Host.

25. Explain NVT (Network Virtual Terminal)
It is a set of rules defining a very simple virtual terminal interaction. The NVT is used in the start of a Telnet session.

26. Explain Gateway-to-Gateway protocol
It is a protocol formerly used to exchange routing information between Internet core routers.

27. Explain BGP (Border Gateway Protocol)
It is a protocol used to advertise the set of networks that can be reached with in an autonomous system. BGP enables this information to be shared with the autonomous system. This is newer than EGP (Exterior Gateway Protocol).

28. Explain autonomous system
It is a collection of routers under the control of a single administrative authority and that uses a common Interior Gateway Protocol.

29. Explain EGP (Exterior Gateway Protocol)
It is the protocol the routers in neighboring autonomous systems use to identify the set of networks that can be reached
within or via each autonomous system.

30. Explain IGP (Interior Gateway Protocol)
It is any routing protocol used within an autonomous system.

31. Explain Mail Gateway
It is a system that performs a protocol translation between different electronic mail delivery protocols.

32. Explain wide-mouth frog
Wide-mouth frog is the simplest known key distribution center (KDC) authentication protocol.

33. What are Digrams and Trigrams
The most common two letter combinations are called as digrams. e.g. th, in, er, re and an. The most common three letter combinations are called as trigrams. e.g. the, ing, and, and ion.

34. Explain silly window syndrome
It is a problem that can ruin TCP performance. This problem occurs when data are passed to the sending TCP entity in large blocks, but an interactive application on the receiving side reads 1 byte at a time.

35. Explain region
When hierarchical routing is used, the routers are divided into what we call regions, with each router knowing all the details about how to route packets to destinations within its own region, but knowing nothing about the internal structure of other regions.

36. Explain multicast routing
Sending a message to a group is called multicasting, and its routing algorithm is called multicast routing.

37. Explain traffic shaping
One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.

38. Explain packet filter
Packet filter is a standard router equipped with some extra functionality. The extra functionality allows every incoming or outgoing packet to be inspected. Packets meeting some criterion are forwarded normally. Those that fail the test are dropped.

39. Explain virtual path
Along any transmission path from a given source to a given destination, a group of virtual circuits can be grouped together into what is called path.

40. Explain virtual channel
Virtual channel is normally a connection from one source to one destination, although multicast connections are also permitted. The other name for virtual channel is virtual circuit.

41. Explain logical link control
One of two sublayers of the data link layer of OSI reference model, as defined by the IEEE 802 standard. This sublayer is responsible for maintaining the link between computers when they are sending data across the physical network connection.

42. Why should you care about the OSI Reference Model
It provides a framework for discussing network operations and design.

43. Explain the difference between routable and non- routable protocols
Routable protocols can work with a router and can be used to build large networks. Non-Routable protocols are designed to work on small, local networks and cannot be used with a router

44. Explain MAU
In token Ring , hub is called Multistation Access Unit(MAU).

45. Explain 5-4-3 rule
In a Ethernet network, between any two points on the network, there can be no more than five network segments or four repeaters, and of those five segments only three of segments can be populated.

46. Explain the difference between TFTP and FTP application layer protocols
The Trivial File Transfer Protocol (TFTP) allows a local host to obtain files from a remote host but does not provide reliability or security. It uses the fundamental packet delivery services offered by UDP.
The File Transfer Protocol (FTP) is the standard mechanism provided by TCP / IP for copying a file from one host to another. It uses the services offered by TCP and so is reliable and secure. It establishes two connections (virtual circuits) between the hosts, one for data transfer and another for control information.

47. Explain the range of addresses in the classes of internet addresses
Class A 0.0.0.0 - 127.255.255.255
Class B 128.0.0.0 - 191.255.255.255
Class C 192.0.0.0 - 223.255.255.255
Class D 224.0.0.0 - 239.255.255.255
Class E 240.0.0.0 - 247.255.255.255

48. Explain the minimum and maximum length of the header in the TCP segment and IP datagram
The header should have a minimum length of 20 bytes and can have a maximum length of 60 bytes.

49. Explain difference between ARP and RARP
The address resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical address, used by a host or a router to find the physical address of another host on its network by sending a ARP query packet that includes the IP address of the receiver. The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.

50. Explain ICMP
ICMP is Internet Control Message Protocol, a network layer protocol of the TCP/IP suite used by hosts and gateways to send notification of datagram problems back to the sender. It uses the echo test / reply to test whether a destination is reachable and responding. It also handles both control and error messages.

51. What are the data units at different layers of the TCP / IP protocol suite
The data unit created at the application layer is called a message, at the transport layer the data unit created is called either a segment or an user datagram, at the network layer the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a frame and
finally transmitted as signals along the transmission media.

52. Explain Project 802
It is a project started by IEEE to set standards that enable intercommunication between equipment from a variety of manufacturers. It is a way for specifying functions of the physical layer, the data link layer and to some extent the network layer to allow for interconnectivity of major LAN protocols.
It consists of the following:
802.1 is an internetworking standard for compatibility of different LANs and MANs across protocols.
802.2 Logical link control (LLC) is the upper sublayer of the data link layer which is non-architecture-specific, that is remains the same for all IEEE-defined LANs.
Media access control (MAC) is the lower sublayer of the data link layer that contains some distinct modules each carrying proprietary information specific to the LAN product being used. The modules are Ethernet LAN (802.3), Token ring LAN (802.4), Token bus LAN (802.5).
802.6 is distributed queue dual bus (DQDB) designed to be used in MANs.

53. Explain Bandwidth
Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range is called the bandwidth.

54. Difference between bit rate and baud rate.
Bit rate is the number of bits transmitted during one second whereas baud rate refers to the number of signal units per second that are required to represent those bits. baud rate = bit rate / N where N is no-of-bits represented by each signal shift.

55. Explain MAC address
The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.

56. Explain attenuation
The degeneration of a signal over distance on a network cable is called attenuation.

57. Explain cladding
A layer of a glass surrounding the center fiber of glass inside a fiber-optic cable.

58. Explain RAID
A method for providing fault tolerance by using multiple hard disk drives.

59. Explain NETBIOS and NETBEUI
NETBIOS is a programming interface that allows I/O requests to be sent to and received from a remote computer and it hides the networking hardware from applications. NETBEUI is NetBIOS extended user interface. A transport protocol designed by microsoft and IBM for the use on small subnets.

60. Explain redirector
Redirector is software that intercepts file or prints I/O requests and translates them into network requests. This comes under presentation layer.

61. Explain Beaconing
The process that allows a network to self-repair networks problems. The stations on the network notify the other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token ring and FDDI networks.
62. Explain terminal emulation, in which layer it comes
Telnet is also called as terminal emulation. It belongs to application layer.

63. Explain frame relay, in which layer it comes
Frame relay is a packet switching technology. It will operate in the data link layer.

64. What do you meant by "triple X" in Networks
The function of PAD (Packet Assembler Disassembler) is described in a document known as X.3. The standard protocol has been defined between the terminal and the PAD, called X.28; another standard protocol exists between hte PAD and the network, called X.29. Together, these three recommendations are often called "triple X"

65. Explain SAP
Series of interface points that allow other computers to communicate with the other layers of network protocol stack.

66. Explain subnet
A generic term for section of a large networks usually separated by a bridge or router.

67. Explain Brouter
Hybrid devices that combine the features of both bridges and routers.

68. How Gateway is different from Routers
A gateway operates at the upper levels of the OSI model and translates information between two completely different network architectures or data formats.

69. What are the different type of networking / internetworking devices
Repeater: Also called a regenerator, it is an electronic device that operates only at physical layer. It receives the signal in the network before it becomes weak, regenerates the original bit pattern and puts the refreshed copy back in to the link.
Bridges: These operate both in the physical and data link layers of LANs of same type. They divide a larger network in to smaller segments. They contain logic that allow them to keep the traffic for each segment separate and thus are repeaters that relay a frame only the side of the segment containing the intended recipent and control congestion.
Routers: They relay packets among multiple interconnected networks (i.e. LANs of different type). They operate in the physical, data link and network layers. They contain software that enable them to determine which of the several possible paths is the best for a particular transmission.
Gateways:
They relay packets among networks that have different protocols (e.g. between a LAN and a WAN). They accept a packet formatted for one protocol and convert it to a packet formatted for another protocol before forwarding it. They operate in all seven layers of the OSI model.

70. Explain mesh network
A network in which there are multiple network links between computers to provide multiple paths for data to travel.

71. Explain passive topology
When the computers on the network simply listen and receive the signal, they are referred to as passive because they don’t amplify the signal in any way. Example for passive topology - linear bus.

72. What are the important topologies for networks
BUS topology:
In this each computer is directly connected to primary network cable in a single line.
Advantages:
Inexpensive, easy to install, simple to understand, easy to extend.
STAR topology:
In this all computers are connected using a central hub.
Advantages:
Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physical problems.
RING topology:
In this all computers are connected in loop.
Advantages:
All computers have equal access to network media, installation can be simple, and signal does not degrade as much as
in other topologies because each computer
regenerates it.

73. What are major types of networks and explain
Server-based network
Peer-to-peer network
Peer-to-peer network, computers can act as both servers sharing resources and as clients using the resources.
Server-based networks provide centralized control of network resources and rely on server computers to provide security and network administration

74. Explain Protocol Data Unit
The data unit in the LLC level is called the protocol data unit (PDU). The PDU contains of four fields a destination service access point (DSAP), a source service access point (SSAP), a control field and an information field. DSAP, SSAP are addresses used by the LLC to identify the protocol stacks on the receiving and sending machines that are generating and using the data. The control field specifies whether the PDU frame is a information frame (I - frame) or a supervisory frame (S - frame) or a
unnumbered frame (U - frame).

75. Explain difference between baseband and broadband transmission
In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal. In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.

76. What are the possible ways of data exchange
(i) Simplex (ii) Half-duplex (iii) Full-duplex.

77. What are the types of Transmission media
Signals are usually transmitted over some transmission media that are broadly classified in to two categories.
Guided Media:
These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept
and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light.
Unguided Media:
This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.

78. Explain point-to-point protocol
A communications protocol used to connect computers to remote networking services including Internet service providers.

79. What are the two types of transmission technology available
(i) Broadcast and (ii) point-to-point

80. Difference between the communication and transmission.
Transmission is a physical movement of information and concern issues like bit polarity, synchronization, clock etc. Communication means the meaning full exchange of information between two communication media.

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2009-04-30T22:54:00.001-07:00

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SERVLETS QUES.

2009-04-30T22:33:00.000-07:00

Question: What is a Servlet?
Answer: Java Servlets are server side components that provides a powerful mechanism for developing server side of web application. Earlier CGI was developed to provide server side capabilities to the web applications. Although CGI played a major role in the explosion of the Internet, its performance, scalability and reusability issues make it less than optimal solutions. Java Servlets changes all that. Built from ground up using Sun's write once run anywhere technology java servlets provide excellent framework for server side processing.

Question: What are the types of Servlet?
Answer: There are two types of servlets, GenericServlet and HttpServlet. GenericServlet defines the generic or protocol independent servlet. HttpServlet is subclass of GenericServlet and provides some http specific functionality linke doGet and doPost methods.

Question: What are the differences between HttpServlet and Generic Servlets?
Answer: HttpServlet Provides an abstract class to be subclassed to create an HTTP servlet suitable for a Web site. A subclass of HttpServlet must override at least one method, usually one of these:

doGet, if the servlet supports HTTP GET requests
doPost, for HTTP POST requests
doPut, for HTTP PUT requests
doDelete, for HTTP DELETE requests
init and destroy, to manage resources that are held for the life of the servlet
getServletInfo, which the servlet uses to provide information about itself
There's almost no reason to override the service method. service handles standard HTTP requests by dispatching them to the handler methods for each HTTP request type (the doXXX methods listed above). Likewise, there's almost no reason to override the doOptions and doTrace methods.

GenericServlet defines a generic, protocol-independent servlet. To write an HTTP servlet for use on the Web, extend HttpServlet instead.

GenericServlet implements the Servlet and ServletConfig interfaces. GenericServlet may be directly extended by a servlet, although it's more common to extend a protocol-specific subclass such as HttpServlet.

GenericServlet makes writing servlets easier. It provides simple versions of the lifecycle methods init and destroy and of the methods in the ServletConfig interface. GenericServlet also implements the log method, declared in the ServletContext interface.

To write a generic servlet, you need only override the abstract service method.

Question: Differentiate between Servlet and Applet.
Answer: Servlets are server side components that executes on the server whereas applets are client side components and executes on the web browser. Applets have GUI interface but there is not GUI interface in case of Servlets.

Question: Differentiate between doGet and doPost method?
Answer: doGet is used when there is are requirement of sending data appended to a query string in the URL. The doGet models the GET method of Http and it is used to retrieve the info on the client from some server as a request to it. The doGet cannot be used to send too much info appended as a query stream. GET puts the form values into the URL string. GET is limited to about 256 characters (usually a browser limitation) and creates really ugly URLs.

POST allows you to have extremely dense forms and pass that to the server without clutter or limitation in size. e.g. you obviously can't send a file from the client to the server via GET. POST has no limit on the amount of data you can send and because the data does not show up on the URL you can send passwords. But this does not mean that POST is truly secure. For real security you have to look into encryption which is an entirely different topic

Question: What are methods of HttpServlet?
Answer: The methods of HttpServlet class are :
* doGet() is used to handle the GET, conditional GET, and HEAD requests
* doPost() is used to handle POST requests
* doPut() is used to handle PUT requests
* doDelete() is used to handle DELETE requests
* doOptions() is used to handle the OPTIONS requests and
* doTrace() is used to handle the TRACE requests

Question: What are the advantages of Servlets over CGI programs?
Answer: Java Servlets have a number of advantages over CGI and other API's. They are:

Platform Independence
Java Servlets are 100% pure Java, so it is platform independence. It can run on any Servlet enabled web server. For example if you develop an web application in windows machine running Java web server. You can easily run the same on apache web server (if Apache Serve is installed) without modification or compilation of code. Platform independency of servlets provide a great advantages over alternatives of servlets.
Performance
Due to interpreted nature of java, programs written in java are slow. But the java servlets runs very fast. These are due to the way servlets run on web server. For any program initialization takes significant amount of time. But in case of servlets initialization takes place very first time it receives a request and remains in memory till times out or server shut downs. After servlet is loaded, to handle a new request it simply creates a new thread and runs service method of servlet. In comparison to traditional CGI scripts which creates a new process to serve the request. This intuitive method of servlets could be use to develop high speed data driven web sites.
Extensibility
Java Servlets are developed in java which is robust, well-designed and object oriented language which can be extended or polymorphed into new objects. So the java servlets takes all these advantages and can be extended from existing class the provide the ideal solutions.
Safety
Java provides a very good safety features like memory management, exception handling etc. Servlets inherits all these features and emerged as a very powerful web server extension.
Secure
Servlets are server side components, so it inherits the security provided by the web server. Servlets are also benefited with Java Security Manager.

Question: What are the lifecycle methods of Servlet?
Answer: The interface javax.servlet.Servlet, defines the three life-cycle methods. These are:
public void init(ServletConfig config) throws ServletException
public void service( ServletRequest req, ServletResponse res) throws ServletException, IOException
public void destroy()
The container manages the lifecycle of the Servlet. When a new request come to a Servlet, the container performs the following steps.
1. If an instance of the servlet does not exist, the web container
* Loads the servlet class.
* Creates an instance of the servlet class.
* Initializes the servlet instance by calling the init method. Initialization is covered in Initializing a Servlet.
2. The container invokes the service method, passing request and response objects.
3. To remove the servlet, container finalizes the servlet by calling the servlet's destroy method.

Question: What are the type of protocols supported by HttpServlet?
Answer: It extends the GenericServlet base class and provides an framework for handling the HTTP protocol. So, HttpServlet only supports HTTP and HTTPS protocol.

Question: What is ServletContext?
Answer: ServletContext is an Interface that defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file. There is one context per "web application" per Java Virtual Machine. (A "web application" is a collection of servlets and content installed under a specific subset of the server's URL namespace such as /catalog and possibly installed via a .war file.)

Question: What is meant by Pre-initialization of Servlet?
Answer: When servlet container is loaded, all the servlets defined in the web.xml file does not initialized by default. But the container receives the request it loads the servlet. But in some cases if you want your servlet to be initialized when context is loaded, you have to use a concept called pre-initialization of Servlet. In case of Pre-initialization, the servlet is loaded when context is loaded. You can specify 1
in between the tag.

Question: What mechanisms are used by a Servlet Container to maintain session information?
Answer: Servlet Container uses Cookies, URL rewriting, and HTTPS protocol information to maintain the session.

Question: What do you understand by servlet mapping?
Answer: Servlet mapping defines an association between a URL pattern and a servlet. You can use one servlet to process a number of url pattern (request pattern). For example in case of Struts *.do url patterns are processed by Struts Controller Servlet.

Question: What must be implemented by all Servlets?
Answer: The Servlet Interface must be implemented by all servlets.

Question: What are the differences between Servlet and Applet?
Answer: Servlets are server side components that runs on the Servlet container. Applets are client side components and runs on the web browsers. Servlets have no GUI interface.

Question: What are the uses of Servlets?
Answer: * Servlets are used to process the client request.
* A Servlet can handle multiple request concurrently and be used to develop high performance system
* A Servlet can be used to load balance among serveral servers, as Servlet can easily forward request.

Question: What are the objects that are received when a servlets accepts call from client?
Answer: The objects are ServeltRequest and ServletResponse . The ServeltRequest encapsulates the communication from the client to the
server. While ServletResponse encapsulates the communication from the Servlet back to the client.

APPLET QUESTIONS

2009-04-30T22:21:00.000-07:00

What is an Applet? Should applets have constructors?

- Applets are small programs transferred through Internet, automatically installed and run as part of web-browser. Applets implements functionality of a client. Applet is a dynamic and interactive program that runs inside a Web page displayed by a Java-capable browser. We don’t have the concept of Constructors in Applets. Applets can be invoked either through browser or through Appletviewer utility provided by JDK.

What are the Applet’s Life Cycle methods? Explain them?

- Following are methods in the life cycle of an Applet:
init() method - called when an applet is first loaded. This method is called only once in the entire cycle of an applet. This method usually intialize the variables to be used in the applet.
start( ) method - called each time an applet is started.
paint() method - called when the applet is minimized or refreshed. This method is used for drawing different strings, figures, and images on the applet window.
stop( ) method - called when the browser moves off the applet’s page.
destroy( ) method - called when the browser is finished with the applet.

What is the sequence for calling the methods by AWT for applets?

- When an applet begins, the AWT calls the following methods, in this sequence:
init()
start()
paint()
When an applet is terminated, the following sequence of method calls takes place :

stop()
destroy()

How do Applets differ from Applications?

- Following are the main differences: Application: Stand Alone, doesn’t need
web-browser. Applet: Needs no explicit installation on local machine. Can be transferred through Internet on to the local machine and may run as part of web-browser. Application: Execution starts with main() method. Doesn’t work if main is not there. Applet: Execution starts with init() method. Application: May or may not be a GUI. Applet: Must run within a GUI (Using AWT). This is essential feature of applets.
Can we pass parameters to an applet from HTML page to an applet? How? - We can pass parameters to an applet using tag in the following way:

Access those parameters inside the applet is done by calling getParameter() method inside the applet. Note that getParameter() method returns String value corresponding to the parameter name.

How do we read number information from my applet’s parameters, given that Applet’s getParameter() method returns a string?

- Use the parseInt() method in the Integer Class, the Float(String) constructor or parseFloat() method in the Class Float, or the
Double(String) constructor or parseDoulbl() method in the class Double.
How can I arrange for different applets on a web page to communicate with each other?
- Name your applets inside the Applet tag and invoke AppletContext’s getApplet() method in your applet code to obtain references to the
other applets on the page.

How do I select a URL from my Applet and send the browser to that page?

- Ask the applet for its applet context and invoke showDocument() on that context object.

URL targetURL;
String URLString
AppletContext context = getAppletContext();
try
{
targetURL = new URL(URLString);
}
catch (MalformedURLException e)
{
// Code for recover from the exception
}
context. showDocument (targetURL);

Can applets on different pages communicate with each other?

- No, Not Directly. The applets will exchange the information at one meeting place either on the local file system or at remote system.

How do I determine the width and height of my application?

- Use the getSize() method, which the Applet class inherits from the Component class in the Java.awt package. The getSize() method returns the size of the applet as a Dimension object, from which you extract separate width, height fields. The following code snippet explains this:

Dimension dim = getSize();
int appletwidth = dim.width();
int appletheight = dim.height();

Which classes and interfaces does Applet class consist?

- Applet class consists of a single class, the Applet class and three interfaces: AppletContext, AppletStub, and AudioClip.

What is AppletStub Interface?

- The applet stub interface provides the means by which an applet and the browser communicate. Your code will not typically implement this interface.
What tags are mandatory when creating HTML to display an applet?
name, height, width
code, name
codebase, height, width
code, height, width
Correct answer is d.

What are the Applet’s information methods?

- The following are the Applet’s information methods: getAppletInfo() method: Returns a string describing the applet, its author, copyright information, etc. getParameterInfo( ) method: Returns an array of string describing the applet’s parameters.

What are the steps involved in Applet development?

- Following are the steps involved in Applet development:
Create/Edit a Java source file. This file must contain a class which extends Applet class.
Compile your program using javac
Execute the appletviewer, specifying the name of your applet’s source file or html file. In case the applet information is stored in html file then Applet can be invoked using java enabled web browser.
Which method is used to output a string to an applet? Which function is this method included in? - drawString( ) method is used to output a string to an applet. This method is included in the paint method of the Applet.

STRUTS QUESTIONS

2009-04-30T06:32:00.000-07:00

What is Struts?
Struts is a web page development framework and an open source software that helps developers build web applications quickly and easily. Struts combines Java Servlets, Java Server Pages, custom tags, and message resources into a unified framework. It is a cooperative, synergistic platform, suitable for development teams, independent developers, and everyone between.

How is the MVC design pattern used in Struts framework?
In the MVC design pattern, application flow is mediated by a central Controller. The Controller delegates requests to an appropriate handler. The handlers are tied to a Model, and each handler acts as an adapter between the request and the Model. The Model represents, or encapsulates, an application's business logic or state. Control is usually then forwarded back through the Controller to the appropriate View. The forwarding can be determined by consulting a set of mappings, usually loaded from a database or configuration file. This provides a loose coupling between the View and Model, which can make an application significantly easier to create and maintain.
Controller--Servlet controller which supplied by Struts itself; View --- what you can see on the screen, a JSP page and presentation components; Model --- System state and a business logic JavaBeans.

Who makes the Struts?
Struts is hosted by the Apache Software Foundation(ASF) as part of its Jakarta project, like Tomcat, Ant and Velocity.

Why it called Struts?
Because the designers want to remind us of the invisible underpinnings that hold up our houses, buildings, bridges, and ourselves when we are on stilts. This excellent description of Struts reflect the role the Struts plays in developing web applications.

Do we need to pay the Struts if being used in commercial purpose?
No. Struts is available for commercial use at no charge under the Apache Software License. You can also integrate the Struts components into your own framework just as if they were written in house without any red tape, fees, or other hassles.

What are the core classes of Struts?
Action, ActionForm, ActionServlet, ActionMapping, ActionForward are basic classes of Structs.

What is the design role played by Struts?
The role played by Structs is controller in Model/View/Controller(MVC) style. The View is played by JSP and Model is played by JDBC or generic data source classes. The Struts controller is a set of programmable components that allow developers to define exactly how the application interacts with the user.

How Struts control data flow?
Struts implements the MVC/Layers pattern through the use of ActionForwards and ActionMappings to keep control-flow decisions out of presentation layer.

What configuration files are used in Struts?
ApplicationResources.properties
struts-config.xml
These two files are used to bridge the gap between the Controller and the Model.

What helpers in the form of JSP pages are provided in Struts framework?
--struts-html.tld
--struts-bean.tld
--struts-logic.tld

Is Struts efficient?
The Struts is not only thread-safe but thread-dependent(instantiates each Action once and allows other requests to be threaded through the original object.
ActionForm beans minimize subclass code and shorten subclass hierarchies
The Struts tag libraries provide general-purpose functionality
The Struts components are reusable by the application
The Struts localization strategies reduce the need for redundant JSPs
The Struts is designed with an open architecture--subclass available
The Struts is lightweight (5 core packages, 5 tag libraries)
The Struts is open source and well documented (code to be examined easily)
The Struts is model neutral

What is ActionServlet?
The class org.apache.struts.action.ActionServlet is the called the ActionServlet. In the the Jakarta Struts Framework this class plays the role of controller. All the requests to the server goes through the controller. Controller is responsible for handling all the requests.

J2EE QUESTIONS2

2009-04-30T06:30:00.001-07:00

What is "abstract schema"
The part of an entity bean's deployment descriptor that defines the bean's persistent fields and relationships.

What is "abstract schema name"
A logical name that is referenced in EJB QL queries.

What is "access control"
The methods by which interactions with resources are limited to collections of users or programs for the purpose of enforcing
integrity, confidentiality, or availability constraints.

What is "ACID"
The acronym for the four properties guaranteed by transactions: atomicity, consistency, isolation, and durability.

What is "activation"
The process of transferring an enterprise bean from secondary storage to memory. (See passivation.) What is "anonymous access"
Accessing a resource without authentication.

What is "applet"
A J2EE component that typically executes in a Web browser but can execute in a variety of other applications or devices that
support the applet programming model.

What is "applet container"
A container that includes support for the applet programming model.

What is "application assembler"
A person who combines J2EE components and modules into deployable application units.

What is "application client"
A first-tier J2EE client component that executes in its own Java virtual machine. Application clients have access to some
J2EE platform APIs.

What is "application client container"
A container that supports application client components. What is "application client module"
A software unit that consists of one or more classes and an application client deployment descriptor.

What is "application component provider"
A vendor that provides the Java classes that implement components' methods, JSP page definitions, and any required deployment
descriptors.

What is "application configuration resource file"
An XML file used to configure resources for a JavaServer Faces application, to define navigation rules for the application,
and to register converters, validators, listeners, renderers, and components with the application.

What is "archiving"
The process of saving the state of an object and restoring it.

What is "asant"
A Java-based build tool that can be extended using Java classes. The configuration files are XML-based, calling out a target
tree where various tasks get executed.

What is "attribute"
A qualifier on an XML tag that provides additional information.
What is authentication
The process that verifies the identity of a user, device, or other entity in a computer system, usually as a prerequisite to
allowing access to resources in a system. The Java servlet specification requires three types of authentication-basic,
form-based, and mutual-and supports digest authentication.

What is authorization
The process by which access to a method or resource is determined. Authorization depends on the determination of whether the
principal associated with a request through authentication is in a given security role. A security role is a logical grouping
of users defined by the person who assembles the application. A deployer maps security roles to security identities. Security
identities may be principals or groups in the operational environment.

What is authorization constraint
An authorization rule that determines who is permitted to access a Web resource collection.

What is B2B
B2B stands for Business-to-business.

What is backing bean
A JavaBeans component that corresponds to a JSP page that includes JavaServer Faces components. The backing bean defines
properties for the components on the page and methods that perform processing for the component. This processing includes
event handling, validation, and processing associated with navigation. What is basic authentication
An authentication mechanism in which a Web server authenticates an entity via a user name and password obtained using the Web
application's built-in authentication mechanism.

What is bean-managed persistence
The mechanism whereby data transfer between an entity bean's variables and a resource manager is managed by the entity bean.

What is bean-managed transaction
A transaction whose boundaries are defined by an enterprise bean.

What is binding (XML)
Generating the code needed to process a well-defined portion of XML data.

What is binding (JavaServer Faces technology)
Wiring UI components to back-end data sources such as backing bean properties.
What is build file
The XML file that contains one or more asant targets. A target is a set of tasks you want to be executed. When starting
asant, you can select which targets you want to have executed. When no target is given, the project's default target is
executed.

What is business logic
The code that implements the functionality of an application. In the Enterprise JavaBeans architecture, this logic is
implemented by the methods of an enterprise bean.

What is business method
A method of an enterprise bean that implements the business logic or rules of an application.

What is callback methods
Component methods called by the container to notify the component of important events in its life cycle.

What is caller
Same as caller principal.

What is caller principal
The principal that identifies the invoker of the enterprise bean method. What is cascade delete
A deletion that triggers another deletion. A cascade delete can be specified for an entity bean that has container-managed
persistence.

What is CDATA
A predefined XML tag for character data that means "don't interpret these characters," as opposed to parsed character data
(PCDATA), in which the normal rules of XML syntax apply. CDATA sections are typically used to show examples of XML syntax.

What is certificate authority
A trusted organization that issues public key certificates and provides identification to the bearer.

What is client-certificate authentication
An authentication mechanism that uses HTTP over SSL, in which the server and, optionally, the client authenticate each other
with a public key certificate that conforms to a standard that is defined by X.509 Public Key Infrastructure.

What is comment
In an XML document, text that is ignored unless the parser is specifically told to recognize it.
What is commit
The point in a transaction when all updates to any resources involved in the transaction are made permanent.

What is component contract
The contract between a J2EE component and its container. The contract includes life-cycle management of the component, a
context interface that the instance uses to obtain various information and services from its container, and a list of
services that every container must provide for its components.

What is component-managed sign-on
A mechanism whereby security information needed for signing on to a resource is provided by an application component.

What is connection factory
See what is resource manager connection factory.

What is connector
A standard extension mechanism for containers that provides connectivity to enterprise information systems. A connector is
specific to an enterprise information system and consists of a resource adapter and application development tools for
enterprise information system connectivity. The resource adapter is plugged in to a container through its support for
system-level contracts defined in the Connector architecture.

What is Connector architecture
An architecture for integration of J2EE products with enterprise information systems. There are two parts to this
architecture: a resource adapter provided by an enterprise information system vendor and the J2EE product that allows this
resource adapter to plug in. This architecture defines a set of contracts that a resource adapter must support to plug in to
a J2EE product-for example, transactions, security, and resource management.

What is container
An entity that provides life-cycle management, security, deployment, and runtime services to J2EE components. Each type of
container (EJB, Web, JSP, servlet, applet, and application client) also provides component-specific services.

What is container-managed persistence
The mechanism whereby data transfer between an entity bean's variables and a resource manager is managed by the entity bean's
container.

What is container-managed sign-on
The mechanism whereby security information needed for signing on to a resource is supplied by the container.

What is container-managed transaction
A transaction whose boundaries are defined by an EJB container. An entity bean must use container-managed transactions.What is content
In an XML document, the part that occurs after the prolog, including the root element and everything it contains.

What is context attribute
An object bound into the context associated with a servlet.

What is context root
A name that gets mapped to the document root of a Web application.

What is conversational state
The field values of a session bean plus the transitive closure of the objects reachable from the bean's fields. The
transitive closure of a bean is defined in terms of the serialization protocol for the Java programming language, that is,
the fields that would be stored by serializing the bean instance.

What is CORBA
Common Object Request Broker Architecture. A language-independent distributed object model specified by the OMG.
What is create method
A method defined in the home interface and invoked by a client to create an enterprise bean.

What is credentials
The information describing the security attributes of a principal.

What is CSS
Cascading style sheet. A stylesheet used with HTML and XML documents to add a style to all elements marked with a particular
tag, for the direction of browsers or other presentation mechanisms.

What is CTS
Compatibility test suite. A suite of compatibility tests for verifying that a J2EE product complies with the J2EE platform
specification.

What is data
The contents of an element in an XML stream, generally used when the element does not contain any subelements. When it does,
the term content is generally used. When the only text in an XML structure is contained in simple elements and when elements
that have subelements have little or no data mixed in, then that structure is often thought of as XML data, as opposed to an
XML document.

What is DDP
Document-driven programming. The use of XML to define applications.

What is declaration
The very first thing in an XML document, which declares it as XML. The minimal declaration is . The
declaration is part of the document prolog.

What is declarative security
Mechanisms used in an application that are expressed in a declarative syntax in a deployment descriptor.

What is delegation
An act whereby one principal authorizes another principal to use its identity or privileges with some restrictions.

What is deployer
A person who installs J2EE modules and applications into an operational environment.

What is deployment
The process whereby software is installed into an operational environment.

What is deployment descriptor
An XML file provided with each module and J2EE application that describes how they should be deployed. The deployment
descriptor directs a deployment tool to deploy a module or application with specific container options and describes specific
configuration requirements that a deployer must resolve. What is destination
A JMS administered object that encapsulates the identity of a JMS queue or topic. See point-to-point messaging system,
publish/subscribe messaging system.

What is digest authentication
An authentication mechanism in which a Web application authenticates itself to a Web server by sending the server a message
digest along with its HTTP request message. The digest is computed by employing a one-way hash algorithm to a concatenation
of the HTTP request message and the client's password. The digest is typically much smaller than the HTTP request and doesn't
contain the password.

What is distributed application
An application made up of distinct components running in separate runtime environments, usually on different platforms
connected via a network. Typical distributed applications are two-tier (client-server), three-tier
(client-middleware-server), and multitier (client-multiple middleware-multiple servers).

What is document
In general, an XML structure in which one or more elements contains text intermixed with subelements. See also data.

What is Document Object Model
An API for accessing and manipulating XML documents as tree structures. DOM provides platform-neutral, language-neutral
interfaces that enables programs and scripts to dynamically access and modify content and structure in XML documents.

What is document root
The top-level directory of a WAR. The document root is where JSP pages, client-side classes and archives, and static Web
resources are stored.

What is DTD
Document type definition. An optional part of the XML document prolog, as specified by the XML standard. The DTD specifies
constraints on the valid tags and tag sequences that can be in the document. The DTD has a number of shortcomings, however,
and this has led to various schema proposals. For example, the DTD entry says that the XML
element called username contains parsed character data-that is, text alone, with no other structural elements under it. The
DTD includes both the local subset, defined in the current file, and the external subset, which consists of the definitions
contained in external DTD files that are referenced in the local subset using a parameter entity.

What is durable subscription
In a JMS publish/subscribe messaging system, a subscription that continues to exist whether or not there is a current active
subscriber object. If there is no active subscriber, the JMS provider retains the subscription's messages until they are
received by the subscription or until they expire.

What is EAR file
Enterprise Archive file. A JAR archive that contains a J2EE application.

What is ebXML
Electronic Business XML. A group of specifications designed to enable enterprises to conduct business through the exchange of
XML-based messages. It is sponsored by OASIS and the United Nations Centre for the Facilitation of Procedures and Practices
in Administration, Commerce and Transport (U.N./CEFACT).

What is EJB
Enterprise JavaBeans.

What is EJB container
A container that implements the EJB component contract of the J2EE architecture. This contract specifies a runtime
environment for enterprise beans that includes security, concurrency, life-cycle management, transactions, deployment,
naming, and other services. An EJB container is provided by an EJB or J2EE server. What is EJB container provider
A vendor that supplies an EJB container.

What is EJB context
An object that allows an enterprise bean to invoke services provided by the container and to obtain the information about the
caller of a client-invoked method.

What is EJB home object
An object that provides the life-cycle operations (create, remove, find) for an enterprise bean. The class for the EJB home
object is generated by the container's deployment tools. The EJB home object implements the enterprise bean's home interface.
The client references an EJB home object to perform life-cycle operations on an EJB object. The client uses JNDI to locate an
EJB home object.

What is EJB JAR file
A JAR archive that contains an EJB module.

What is EJB module
A deployable unit that consists of one or more enterprise beans and an EJB deployment descriptor.

What is EJB object
An object whose class implements the enterprise bean's remote interface. A client never references an enterprise bean
instance directly; a client always references an EJB object. The class of an EJB object is generated by a container's
deployment tools.

What is EJB server
Software that provides services to an EJB container. For example, an EJB container typically relies on a transaction manager
that is part of the EJB server to perform the two-phase commit across all the participating resource managers. The J2EE
architecture assumes that an EJB container is hosted by an EJB server from the same vendor, so it does not specify the
contract between these two entities. An EJB server can host one or more EJB containers.

What is EJB server provider
A vendor that supplies an EJB server.

What is element
A unit of XML data, delimited by tags. An XML element can enclose other elements.

What is empty tag
A tag that does not enclose any content.

What is enterprise bean
A J2EE component that implements a business task or business entity and is hosted by an EJB container; either an entity bean,
a session bean, or a message-driven bean.

What is enterprise bean provider
An application developer who produces enterprise bean classes, remote and home interfaces, and deployment descriptor files,
and packages them in an EJB JAR file.

What is enterprise information system
The applications that constitute an enterprise's existing system for handling companywide information. These applications
provide an information infrastructure for an enterprise. An enterprise information system offers a well-defined set of
services to its clients. These services are exposed to clients as local or remote interfaces or both. Examples of enterprise
information systems include enterprise resource planning systems, mainframe transaction processing systems, and legacy
database systems.

What is enterprise information system resource
An entity that provides enterprise information system-specific functionality to its clients. Examples are a record or set of
records in a database system, a business object in an enterprise resource planning system, and a transaction program in a
transaction processing system.

What is Enterprise JavaBeans (EJB)
A component architecture for the development and deployment of object-oriented, distributed, enterprise-level applications.
Applications written using the Enterprise JavaBeans architecture are scalable, transactional, and secure.

What is Enterprise JavaBeans Query Language (EJB QL)
Defines the queries for the finder and select methods of an entity bean having container-managed persistence. A subset of
SQL92, EJB QL has extensions that allow navigation over the relationships defined in an entity bean's abstract schema.

What is an entity
A distinct, individual item that can be included in an XML document by referencing it. Such an entity reference can name an
entity as small as a character (for example, <, which references the less-than symbol or left angle bracket, <). An entity
reference can also reference an entire document, an external entity, or a collection of DTD definitions.

What is entity bean
An enterprise bean that represents persistent data maintained in a database. An entity bean can manage its own persistence or
can delegate this function to its container. An entity bean is identified by a primary key. If the container in which an
entity bean is hosted crashes, the entity bean, its primary key, and any remote references survive the crash.

What is entity reference
A reference to an entity that is substituted for the reference when the XML document is parsed. It can reference a predefined
entity such as < or reference one that is defined in the DTD. In the XML data, the reference could be to an entity that is
defined in the local subset of the DTD or to an external XML file (an external entity). The DTD can also carve out a segment
of DTD specifications and give it a name so that it can be reused (included) at multiple points in the DTD by defining a
parameter entity.

What is error
A SAX parsing error is generally a validation error; in other words, it occurs when an XML document is not valid, although it
can also occur if the declaration specifies an XML version that the parser cannot handle. See also fatal error, warning.

What is Extensible Markup Language
XML.

What is external entity
An entity that exists as an external XML file, which is included in the XML document using an entity reference.

What is external subset
That part of a DTD that is defined by references to external DTD files.

What is fatal error
A fatal error occurs in the SAX parser when a document is not well formed or otherwise cannot be processed. See also error,
warning.
What is filter
An object that can transform the header or content (or both) of a request or response. Filters differ from Web components in
that they usually do not themselves create responses but rather modify or adapt the requests for a resource, and modify or
adapt responses from a resource. A filter should not have any dependencies on a Web resource for which it is acting as a
filter so that it can be composable with more than one type of Web resource.

What is filter chain
A concatenation of XSLT transformations in which the output of one transformation becomes the input of the next.

What is finder method
A method defined in the home interface and invoked by a client to locate an entity bean.

What is form-based authentication
An authentication mechanism in which a Web container provides an application-specific form for logging in. This form of
authentication uses Base64 encoding and can expose user names and passwords unless all connections are over SSL.

What is general entity
An entity that is referenced as part of an XML document's content, as distinct from a parameter entity, which is referenced
in the DTD. A general entity can be a parsed entity or an unparsed entity.

What is group
An authenticated set of users classified by common traits such as job title or customer profile. Groups are also associated
with a set of roles, and every user that is a member of a group inherits all the roles assigned to that group.

What is handle
An object that identifies an enterprise bean. A client can serialize the handle and then later deserialize it to obtain a
reference to the enterprise bean. What is home handle
An object that can be used to obtain a reference to the home interface. A home handle can be serialized and written to stable
storage and deserialized to obtain the reference.

What is home interface
One of two interfaces for an enterprise bean. The home interface defines zero or more methods for managing an enterprise
bean. The home interface of a session bean defines create and remove methods, whereas the home interface of an entity bean
defines create, finder, and remove methods.

What is HTML
Hypertext Markup Language. A markup language for hypertext documents on the Internet. HTML enables the embedding of images,
sounds, video streams, form fields, references to other objects with URLs, and basic text formatting.

What is HTTP
Hypertext Transfer Protocol. The Internet protocol used to retrieve hypertext objects from remote hosts. HTTP messages
consist of requests from client to server and responses from server to client.

What is HTTPS
HTTP layered over the SSL protocol.

What is IDL
Interface Definition Language. A language used to define interfaces to remote CORBA objects. The interfaces are independent
of operating systems and programming languages.

What is IIOP
Internet Inter-ORB Protocol. A protocol used for communication between CORBA object request brokers.

What is impersonation
An act whereby one entity assumes the identity and privileges of another entity without restrictions and without any
indication visible to the recipients of the impersonator's calls that delegation has taken place. Impersonation is a case of
simple delegation. What is initialization parameter
A parameter that initializes the context associated with a servlet.

What is ISO 3166
The international standard for country codes maintained by the International Organization for Standardization (ISO).

What is ISV
Independent software vendor.

What is J2EE
Java 2 Platform, Enterprise Edition.

What is J2EE application
Any deployable unit of J2EE functionality. This can be a single J2EE module or a group of modules packaged into an EAR file along with a J2EE application deployment descriptor. J2EE applications are typically engineered to be distributed across multiple computing tiers.

What is J2EE component
A self-contained functional software unit supported by a container and configurable at deployment time. The J2EE specification defines the following J2EE components:
Application clients and applets are components that run on the client.
Java servlet and JavaServer Pages (JSP) technology components are Web components that run on the server.
Enterprise JavaBeans (EJB) components (enterprise beans) are business components that run on the server.
J2EE components are written in the Java programming language and are compiled in the same way as any program in the language. The difference between J2EE components and "standard" Java classes is that J2EE components are assembled into a J2EE application, verified to be well formed and in compliance with the J2EE specification, and deployed to production, where they are run and managed by the J2EE server or client container.

What is J2EE module
A software unit that consists of one or more J2EE components of the same container type and one deployment descriptor of that type. There are four types of modules: EJB, Web, application client, and resource adapter. Modules can be deployed as stand-alone units or can be assembled into a J2EE application.

What is J2EE product
An implementation that conforms to the J2EE platform specification.

What is J2EE product provider
A vendor that supplies a J2EE product.

What is J2EE server
The runtime portion of a J2EE product. A J2EE server provides EJB or Web containers or both.

What is J2ME
Abbreviate of Java 2 Platform, Micro Edition.

What is J2SE
Abbreviate of Java 2 Platform, Standard Edition.

What is JAR
Java archive. A platform-independent file format that permits many files to be aggregated into one file. What is Java 2 Platform, Enterprise Edition (J2EE)
An environment for developing and deploying enterprise applications. The J2EE platform consists of a set of services, application programming interfaces (APIs), and protocols that provide the functionality for developing multitiered, Web-based applications.

What is Java 2 Platform, Micro Edition (J2ME)
A highly optimized Java runtime environment targeting a wide range of consumer products, including pagers, cellular phones, screen phones, digital set-top boxes, and car navigation systems.

What is Java 2 Platform, Standard Edition (J2SE)
The core Java technology platform.

What is Java API for XML Processing (JAXP)
An API for processing XML documents. JAXP leverages the parser standards SAX and DOM so that you can choose to parse your data as a stream of events or to build a tree-structured representation of it. JAXP supports the XSLT standard, giving you control over the presentation of the data and enabling you to convert the data to other XML documents or to other formats, such as HTML. JAXP provides namespace support, allowing you to work with schema that might otherwise have naming conflicts.

What is Java API for XML Registries (JAXR)
An API for accessing various kinds of XML registries.

What is Java API for XML-based RPC (JAX-RPC)
An API for building Web services and clients that use remote procedure calls and XML. What is Java IDL
A technology that provides CORBA interoperability and connectivity capabilities for the J2EE platform. These capabilities enable J2EE applications to invoke operations on remote network services using the Object Management Group IDL and IIOP.

What is Java Message Service (JMS)
An API for invoking operations on enterprise messaging systems.

What is Java Naming and Directory Interface (JNDI)
An API that provides naming and directory functionality.

What is Java Secure Socket Extension (JSSE)
A set of packages that enable secure Internet communications.

What is Java Transaction API (JTA)
An API that allows applications and J2EE servers to access transactions.

What is Java Transaction Service (JTS)
Specifies the implementation of a transaction manager that supports JTA and implements the Java mapping of the Object Management Group Object Transaction Service 1.1 specification at the level below the API.

What is JavaBeans component
A Java class that can be manipulated by tools and composed into applications. A JavaBeans component must adhere to certain property and event interface conventions.
What is JavaMail
An API for sending and receiving email.

What is JavaServer Faces Technology
A framework for building server-side user interfaces for Web applications written in the Java programming language.

What is JavaServer Faces conversion model
A mechanism for converting between string-based markup generated by JavaServer Faces UI components and server-side Java objects.

What is JavaServer Faces event and listener model
A mechanism for determining how events emitted by JavaServer Faces UI components are handled. This model is based on the JavaBeans component event and listener model.

What is JavaServer Faces expression language
A simple expression language used by a JavaServer Faces UI component tag attributes to bind the associated component to a bean property or to bind the associated component's value to a method or an external data source, such as a bean property. Unlike JSP EL expressions, JavaServer Faces EL expressions are evaluated by the JavaServer Faces implementation rather than by the Web container.

What is JavaServer Faces navigation model
A mechanism for defining the sequence in which pages in a JavaServer Faces application are displayed.

What is JavaServer Faces UI component
A user interface control that outputs data to a client or allows a user to input data to a JavaServer Faces application.
What is JavaServer Faces UI component class
A JavaServer Faces class that defines the behavior and properties of a JavaServer Faces UI component.

What is JavaServer Faces validation model
A mechanism for validating the data a user inputs to a JavaServer Faces UI component.

What is JavaServer Pages (JSP)
An extensible Web technology that uses static data, JSP elements, and server-side Java objects to generate dynamic content for a client. Typically the static data is HTML or XML elements, and in many cases the client is a Web browser.

What is JavaServer Pages Standard Tag Library (JSTL)
A tag library that encapsulates core functionality common to many JSP applications. JSTL has support for common, structural tasks such as iteration and conditionals, tags for manipulating XML documents, internationalization and locale-specific formatting tags, SQL tags, and functions.

What is JAXR client
A client program that uses the JAXR API to access a business registry via a JAXR provider.

What is JAXR provider
An implementation of the JAXR API that provides access to a specific registry provider or to a class of registry providers that are based on a common specification.

What is JDBC
An API for database-independent connectivity between the J2EE platform and a wide range of data sources.

What is JMS
Java Message Service.

What is JMS administered object
A preconfigured JMS object (a resource manager connection factory or a destination) created by an administrator for the use of JMS clients and placed in a JNDI namespace.

What is JMS application
One or more JMS clients that exchange messages.

What is JMS client
A Java language program that sends or receives messages.

What is JMS provider
A messaging system that implements the Java Message Service as well as other administrative and control functionality needed in a full-featured messaging product.

What is JMS session
A single-threaded context for sending and receiving JMS messages. A JMS session can be nontransacted, locally transacted, or participating in a distributed transaction.

What is JNDI
Abbreviate of Java Naming and Directory Interface.

What is JSP
Abbreviate of JavaServer Pages.

What is JSP action
A JSP element that can act on implicit objects and other server-side objects or can define new scripting variables. Actions follow the XML syntax for elements, with a start tag, a body, and an end tag; if the body is empty it can also use the empty tag syntax. The tag must use a prefix. There are standard and custom actions.
What is JSP container
A container that provides the same services as a servlet container and an engine that interprets and processes JSP pages into a servlet.

What is JSP container, distributed
A JSP container that can run a Web application that is tagged as distributable and is spread across multiple Java virtual machines that might be running on different hosts.

What is JSP custom action
A user-defined action described in a portable manner by a tag library descriptor and imported into a JSP page by a taglib directive. Custom actions are used to encapsulate recurring tasks in writing JSP pages.

What is JSP custom tag
A tag that references a JSP custom action.

What is JSP declaration
A JSP scripting element that declares methods, variables, or both in a JSP page.

What is JSP directive
A JSP element that gives an instruction to the JSP container and is interpreted at translation time.

What is JSP document
A JSP page written in XML syntax and subject to the constraints of XML documents.
What is JSP element
A portion of a JSP page that is recognized by a JSP translator. An element can be a directive, an action, or a scripting element.

What is JSP expression
A scripting element that contains a valid scripting language expression that is evaluated, converted to a String, and placed into the implicit out object.

What is JSP expression language
A language used to write expressions that access the properties of JavaBeans components. EL expressions can be used in static text and in any standard or custom tag attribute that can accept an expression.

What is JSP page
A text-based document containing static text and JSP elements that describes how to process a request to create a response. A JSP page is translated into and handles requests as a servlet.

What is JSP scripting element
A JSP declaration, scriptlet, or expression whose syntax is defined by the JSP specification and whose content is written according to the scripting language used in the JSP page. The JSP specification describes the syntax and semantics for the case where the language page attribute is "java".

What is JSP scriptlet
A JSP scripting element containing any code fragment that is valid in the scripting language used in the JSP page. The JSP specification describes what is a valid scriptlet for the case where the language page attribute is "java".

What is JSP standard action
An action that is defined in the JSP specification and is always available to a JSP page.
What is JSP tag file
A source file containing a reusable fragment of JSP code that is translated into a tag handler when a JSP page is translated into a servlet.

What is JSP tag handler
A Java programming language object that implements the behavior of a custom tag.

What is JSP tag library
A collection of custom tags described via a tag library descriptor and Java classes.

What is JSTL
Abbreviate of JavaServer Pages Standard Tag Library.

What is JTA
Abbreviate of Java Transaction API.

What is JTS
Abbreviate of Java Transaction Service.

What is keystore
A file containing the keys and certificates used for authentication. What is life cycle (J2EE component)
The framework events of a J2EE component's existence. Each type of component has defining events that mark its transition into states in which it has varying availability for use. For example, a servlet is created and has its init method called by its container before invocation of its service method by clients or other servlets that require its functionality. After the call of its init method, it has the data and readiness for its intended use. The servlet's destroy method is called by its container before the ending of its existence so that processing associated with winding up can be done and resources can be released. The init and destroy methods in this example are callback methods. Similar considerations apply to the life cycle of all J2EE component types: enterprise beans, Web components (servlets or JSP pages), applets, and application clients.

What is life cycle (JavaServer Faces)
A set of phases during which a request for a page is received, a UI component tree representing the page is processed, and a response is produced. During the phases of the life cycle:
The local data of the components is updated with the values contained in the request parameters.
Events generated by the components are processed.
Validators and converters registered on the components are processed.
The components' local data is updated to back-end objects.
The response is rendered to the client while the component state of the response is saved on the server for future requests.

What is local subset
That part of the DTD that is defined within the current XML file.

What is managed bean creation facility
A mechanism for defining the characteristics of JavaBeans components used in a JavaServer Faces application.

What is message
In the Java Message Service, an asynchronous request, report, or event that is created, sent, and consumed by an enterprise application and not by a human. It contains vital information needed to coordinate enterprise applications, in the form of precisely formatted data that describes specific business actions.

What is message consumer
An object created by a JMS session that is used for receiving messages sent to a destination.

What is message-driven bean
An enterprise bean that is an asynchronous message consumer. A message-driven bean has no state for a specific client, but its instance variables can contain state across the handling of client messages, including an open database connection and an object reference to an EJB object. A client accesses a message-driven bean by sending messages to the destination for which the bean is a message listener.

What is message producer
An object created by a JMS session that is used for sending messages to a destination.
What is mixed-content model
A DTD specification that defines an element as containing a mixture of text and one more other elements. The specification must start with #PCDATA, followed by diverse elements, and must end with the "zero-or-more" asterisk symbol (*).

What is method-binding expression
A JavaServer Faces EL expression that refers to a method of a backing bean. This method performs either event handling, validation, or navigation processing for the UI component whose tag uses the method-binding expression.

What is method permission
An authorization rule that determines who is permitted to execute one or more enterprise bean methods.

What is mutual authentication
An authentication mechanism employed by two parties for the purpose of proving each other's identity to one another.

What is namespace
A standard that lets you specify a unique label for the set of element names defined by a DTD. A document using that DTD can be included in any other document without having a conflict between element names. The elements defined in your DTD are then uniquely identified so that, for example, the parser can tell when an element should be interpreted according to your DTD rather than using the definition for an element in a different DTD.

What is naming context
A set of associations between unique, atomic, people-friendly identifiers and objects.

What is naming environment
A mechanism that allows a component to be customized without the need to access or change the component's source code. A container implements the component's naming environment and provides it to the component as a JNDI naming context. Each component names and accesses its environment entries using the java:comp/env JNDI context. The environment entries are declaratively specified in the component's deployment descriptor.

What is normalization
The process of removing redundancy by modularizing, as with subroutines, and of removing superfluous differences by reducing them to a common denominator. For example, line endings from different systems are normalized by reducing them to a single new line, and multiple whitespace characters are normalized to one space.

What is North American Industry Classification System (NAICS)
A system for classifying business establishments based on the processes they use to produce goods or services.

What is notation
A mechanism for defining a data format for a non-XML document referenced as an unparsed entity. This is a holdover from SGML. A newer standard is to use MIME data types and namespaces to prevent naming conflicts.

What is OASIS
Organization for the Advancement of Structured Information Standards. A consortium that drives the development, convergence, and adoption of e-business standards. Its Web site is http://www.oasis-open.org/. The DTD repository it sponsors is at http://www.XML.org.

What is OMG
Object Management Group. A consortium that produces and maintains computer industry specifications for interoperable enterprise applications.
What is one-way messaging
A method of transmitting messages without having to block until a response is received.

What is ORB
Object request broker. A library that enables CORBA objects to locate and communicate with one another. What is OS principal
A principal native to the operating system on which the J2EE platform is executing.

What is OTS
Object Transaction Service. A definition of the interfaces that permit CORBA objects to participate in transactions.

What is parameter entity
An entity that consists of DTD specifications, as distinct from a general entity. A parameter entity defined in the DTD can then be referenced at other points, thereby eliminating the need to recode the definition at each location it is used.

What is parsed entity
A general entity that contains XML and therefore is parsed when inserted into the XML document, as opposed to an unparsed entity.

What is parser
A module that reads in XML data from an input source and breaks it into chunks so that your program knows when it is working with a tag, an attribute, or element data. A nonvalidating parser ensures that the XML data is well formed but does not verify that it is valid. See also validating parser.

What is passivation
The process of transferring an enterprise bean from memory to secondary storage. See activation.

What is persistence
The protocol for transferring the state of an entity bean between its instance variables and an underlying database.
What is persistent field
A virtual field of an entity bean that has container-managed persistence; it is stored in a database.

What is POA
Portable Object Adapter. A CORBA standard for building server-side applications that are portable across heterogeneous ORBs.

What is point-to-point messaging system
A messaging system built on the concept of message queues. Each message is addressed to a specific queue; clients extract messages from the queues established to hold their messages.

What is primary key
An object that uniquely identifies an entity bean within a home.

What is principal
The identity assigned to a user as a result of authentication.

What is privilege
A security attribute that does not have the property of uniqueness and that can be shared by many principals.

What is processing instruction
Information contained in an XML structure that is intended to be interpreted by a specific application.

What is programmatic security
Security decisions that are made by security-aware applications. Programmatic security is useful when declarative security alone is not sufficient to express the security model of an application.

What is prolog
The part of an XML document that precedes the XML data. The prolog includes the declaration and an optional DTD.

What is public key certificate
Used in client-certificate authentication to enable the server, and optionally the client, to authenticate each other. The public key certificate is the digital equivalent of a passport. It is issued by a trusted organization, called a certificate authority, and provides identification for the bearer.

What is publish/subscribe messaging system
A messaging system in which clients address messages to a specific node in a content hierarchy, called a topic. Publishers and subscribers are generally anonymous and can dynamically publish or subscribe to the content hierarchy. The system takes care of distributing the messages arriving from a node's multiple publishers to its multiple subscribers.

What is query string
A component of an HTTP request URL that contains a set of parameters and values that affect the handling of the request.

What is queue
See point-to-point messaging system.

What is RAR
Resource Adapter Archive. A JAR archive that contains a resource adapter module.

What is RDF
Resource Description Framework. A standard for defining the kind of data that an XML file contains. Such information can help ensure semantic integrity-for example-by helping to make sure that a date is treated as a date rather than simply as text.

What is RDF schema
A standard for specifying consistency rules that apply to the specifications contained in an RDF.

What is realm
See security policy domain. Also, a string, passed as part of an HTTP request during basic authentication, that defines a protection space. The protected resources on a server can be partitioned into a set of protection spaces, each with its own authentication scheme or authorization database or both.
In the J2EE server authentication service, a realm is a complete database of roles, users, and groups that identify valid users of a Web application or a set of Web applications.

What is reentrant entity bean
An entity bean that can handle multiple simultaneous, interleaved, or nested invocations that will not interfere with each other.

What is registry
An infrastructure that enables the building, deployment, and discovery of Web services. It is a neutral third party that facilitates dynamic and loosely coupled business-to-business (B2B) interactions.
What is registry provider
An implementation of a business registry that conforms to a specification for XML registries (for example, ebXML or UDDI).

What is relationship field
A virtual field of an entity bean having container-managed persistence; it identifies a related entity bean.

What is remote interface
One of two interfaces for an enterprise bean. The remote interface defines the business methods callable by a client.

What is remove method
Method defined in the home interface and invoked by a client to destroy an enterprise bean.

What is render kit
A set of renderers that render output to a particular client. The JavaServer Faces implementation provides a standard HTML render kit, which is composed of renderers that can render HMTL markup.

What is renderer
A Java class that can render the output for a set of JavaServer Faces UI components.

What is request-response messaging
A method of messaging that includes blocking until a response is received.What is resource adapter
A system-level software driver that is used by an EJB container or an application client to connect to an enterprise information system. A resource adapter typically is specific to an enterprise information system. It is available as a library and is used within the address space of the server or client using it. A resource adapter plugs in to a container. The application components deployed on the container then use the client API (exposed by the adapter) or tool-generated high-level abstractions to access the underlying enterprise information system. The resource adapter and EJB container collaborate to provide the underlying mechanisms-transactions, security, and connection pooling-for connectivity to the enterprise information system.

What is resource adapter module
A deployable unit that contains all Java interfaces, classes, and native libraries, implementing a resource adapter along with the resource adapter deployment descriptor.

What is resource manager
Provides access to a set of shared resources. A resource manager participates in transactions that are externally controlled and coordinated by a transaction manager. A resource manager typically is in a different address space or on a different machine from the clients that access it. Note: An enterprise information system is referred to as a resource manager when it is mentioned in the context of resource and transaction management.

What is resource manager connection
An object that represents a session with a resource manager.

What is resource manager connection factory
An object used for creating a resource manager connection.

What is RMI
Remote Method Invocation. A technology that allows an object running in one Java virtual machine to invoke methods on an object running in a different Java virtual machine.

What is RMI-IIOP
A version of RMI implemented to use the CORBA IIOP protocol. RMI over IIOP provides interoperability with CORBA objects implemented in any language if all the remote interfaces are originally defined as RMI interfaces.
What is role (development)
The function performed by a party in the development and deployment phases of an application developed using J2EE technology. The roles are application component provider, application assembler, deployer, J2EE product provider, EJB container provider, EJB server provider, Web container provider, Web server provider, tool provider, and system administrator.

What is role mapping
The process of associating the groups or principals (or both), recognized by the container with security roles specified in the deployment descriptor. Security roles must be mapped by the deployer before a component is installed in the server.

What is role (security)
An abstract logical grouping of users that is defined by the application assembler. When an application is deployed, the roles are mapped to security identities, such as principals or groups, in the operational environment.
In the J2EE server authentication service, a role is an abstract name for permission to access a particular set of resources. A role can be compared to a key that can open a lock. Many people might have a copy of the key; the lock doesn't care who you are, only that you have the right key.

What is rollback
The point in a transaction when all updates to any resources involved in the transaction are reversed.

What is root
The outermost element in an XML document. The element that contains all other elements.

What is SAX
Abbreviation of Simple API for XML.

What is Simple API for XML
An event-driven interface in which the parser invokes one of several methods supplied by the caller when a parsing event occurs. Events include recognizing an XML tag, finding an error, encountering a reference to an external entity, or processing a DTD specification.

What is schema
A database-inspired method for specifying constraints on XML documents using an XML-based language. Schemas address deficiencies in DTDs, such as the inability to put constraints on the kinds of data that can occur in a particular field. Because schemas are founded on XML, they are hierarchical. Thus it is easier to create an unambiguous specification, and it is possible to determine the scope over which a comment is meant to apply.

What is Secure Socket Layer (SSL)
A technology that allows Web browsers and Web servers to communicate over a secured connection.

What is security attributes
A set of properties associated with a principal. Security attributes can be associated with a principal by an authentication protocol or by a J2EE product provider or both.

What is security constraint
A declarative way to annotate the intended protection of Web content. A security constraint consists of a Web resource collection, an authorization constraint, and a user data constraint.

What is security context
An object that encapsulates the shared state information regarding security between two entities.

What is security permission
A mechanism defined by J2SE, and used by the J2EE platform to express the programming restrictions imposed on application component developers.

What is security permission set
The minimum set of security permissions that a J2EE product provider must provide for the execution of each component type.
What is security policy domain
A scope over which security policies are defined and enforced by a security administrator. A security policy domain has a collection of users (or principals), uses a well-defined authentication protocol or protocols for authenticating users (or principals), and may have groups to simplify setting of security policies.

What is security technology domain
A scope over which the same security mechanism is used to enforce a security policy. Multiple security policy domains can exist within a single technology domain.

What is security view
The set of security roles defined by the application assembler.

What is server certificate
Used with the HTTPS protocol to authenticate Web applications. The certificate can be self-signed or approved by a certificate authority (CA). The HTTPS service of the Sun Java System Application Server Platform Edition 8 will not run unless a server certificate has been installed.

What is server principal
The OS principal that the server is executing as.

What is service element
A representation of the combination of one or more Connector components that share a single engine component for processing incoming requests.
What is service endpoint interface
A Java interface that declares the methods that a client can invoke on a Web service.

What is servlet
A Java program that extends the functionality of a Web server, generating dynamic content and interacting with Web applications using a request-response paradigm.

What is servlet container
A container that provides the network services over which requests and responses are sent, decodes requests, and formats responses. All servlet containers must support HTTP as a protocol for requests and responses but can also support additional request-response protocols, such as HTTPS.

What is servlet container, distributed
A servlet container that can run a Web application that is tagged as distributable and that executes across multiple Java virtual machines running on the same host or on different hosts.

What is servlet context
An object that contains a servlet's view of the Web application within which the servlet is running. Using the context, a servlet can log events, obtain URL references to resources, and set and store attributes that other servlets in the context can use.

What is servlet mapping
Defines an association between a URL pattern and a servlet. The mapping is used to map requests to servlets.

What is session
An object used by a servlet to track a user's interaction with a Web application across multiple HTTP requests. What is session bean
An enterprise bean that is created by a client and that usually exists only for the duration of a single client-server session. A session bean performs operations, such as calculations or database access, for the client. Although a session bean can be transactional, it is not recoverable should a system crash occur. Session bean objects either can be stateless or can maintain conversational state across methods and transactions. If a session bean maintains state, then the EJB container manages this state if the object must be removed from memory. However, the session bean object itself must manage its own persistent data.

What is SGML
Standard Generalized Markup Language. The parent of both HTML and XML. Although HTML shares SGML's propensity for embedding presentation information in the markup, XML is a standard that allows information content to be totally separated from the mechanisms for rendering that content.

What is SOAP
Simple Object Access Protocol. A lightweight protocol intended for exchanging structured information in a decentralized, distributed environment. It defines, using XML technologies, an extensible messaging framework containing a message construct that can be exchanged over a variety of underlying protocols.

What is SOAP with Attachments API for Java (SAAJ)
The basic package for SOAP messaging, SAAJ contains the API for creating and populating a SOAP message.

What is SQL
Structured Query Language. The standardized relational database language for defining database objects and manipulating data.

What is SQL/J
A set of standards that includes specifications for embedding SQL statements in methods in the Java programming language and specifications for calling Java static methods as SQL stored procedures and user-defined functions. An SQL checker can detect errors in static SQL statements at program development time, rather than at execution time as with a JDBC driver.

What is SSL
Secure Socket Layer. A security protocol that provides privacy over the Internet. The protocol allows client-server applications to communicate in a way that cannot be eavesdropped upon or tampered with. Servers are always authenticated, and clients are optionally authenticated.

What is stateful session bean
A session bean with a conversational state.

What is stateless session bean
A session bean with no conversational state. All instances of a stateless session bean are identical.

What is system administrator
The person responsible for configuring and administering the enterprise's computers, networks, and software systems.

What is tag
In XML documents, a piece of text that describes a unit of data or an element. The tag is distinguishable as markup, as opposed to data, because it is surrounded by angle brackets (< and >). To treat such markup syntax as data, you use an entity reference or a CDATA section.

What is template
A set of formatting instructions that apply to the nodes selected by an XPath expression.

What is tool provider
An organization or software vendor that provides tools used for the development, packaging, and deployment of J2EE applications.What is topic
See publish-subscribe messaging system.

What is transaction
An atomic unit of work that modifies data. A transaction encloses one or more program statements, all of which either complete or roll back. Transactions enable multiple users to access the same data concurrently.

What is transaction attribute
A value specified in an enterprise bean's deployment descriptor that is used by the EJB container to control the transaction scope when the enterprise bean's methods are invoked. A transaction attribute can have the following values: Required, RequiresNew, Supports, NotSupported, Mandatory, or Never.

What is transaction isolation level
The degree to which the intermediate state of the data being modified by a transaction is visible to other concurrent transactions and data being modified by other transactions is visible to it.

What is transaction manager
Provides the services and management functions required to support transaction demarcation, transactional resource management, synchronization, and transaction context propagation.

What is Unicode
A standard defined by the Unicode Consortium that uses a 16-bit code page that maps digits to characters in languages around the world. Because 16 bits covers 32,768 codes, Unicode is large enough to include all the world's languages, with the exception of ideographic languages that have a different character for every concept, such as Chinese.

What is Universal Description, Discovery and Integration (UDDI) project
An industry initiative to create a platform-independent, open framework for describing services, discovering businesses, and integrating business services using the Internet, as well as a registry. It is being developed by a vendor consortium.

What is Universal Standard Products and Services Classification (UNSPSC)
A schema that classifies and identifies commodities. It is used in sell-side and buy-side catalogs and as a standardized account code in analyzing expenditure.

What is unparsed entity
A general entity that contains something other than XML. By its nature, an unparsed entity contains binary data.

What is URI
Uniform resource identifier. A globally unique identifier for an abstract or physical resource. A URL is a kind of URI that specifies the retrieval protocol (http or https for Web applications) and physical location of a resource (host name and host-relative path). A URN is another type of URI.

What is URL
Uniform resource locator. A standard for writing a textual reference to an arbitrary piece of data in the World Wide Web. A URL looks like this: protocol://host/localinfo where protocol specifies a protocol for fetching the object (such as http or ftp), host specifies the Internet name of the targeted host, and localinfo is a string (often a file name) passed to the protocol handler on the remote host.

What is URL path
The part of a URL passed by an HTTP request to invoke a servlet. A URL path consists of the context path + servlet path + path info, where Context path is the path prefix associated with a servlet context of which the servlet is a part. If this context is the default context rooted at the base of the Web server's URL namespace, the path prefix will be an empty string. Otherwise, the path prefix starts with a / character but does not end with a / character.
Servlet path is the path section that directly corresponds to the mapping that activated this request. This path starts with a / character.
Path info is the part of the request path that is not part of the context path or the servlet path.

What is URN
Uniform resource name. A unique identifier that identifies an entity but doesn't tell where it is located. A system can use a URN to look up an entity locally before trying to find it on the Web. It also allows the Web location to change, while still allowing the entity to be found.

What is user data constraint
Indicates how data between a client and a Web container should be protected. The protection can be the prevention of tampering with the data or prevention of eavesdropping on the data.

What is user (security)
An individual (or application program) identity that has been authenticated. A user can have a set of roles associated with that identity, which entitles the user to access all resources protected by those roles.

What is valid
A valid XML document, in addition to being well formed, conforms to all the constraints imposed by a DTD. It does not contain any tags that are not permitted by the DTD, and the order of the tags conforms to the DTD's specifications.

What is validating parser
A parser that ensures that an XML document is valid in addition to being well formed. See also parser.

What is value-binding expression
A JavaServer Faces EL expression that refers to a property of a backing bean. A component tag uses this expression to bind the associated component's value or the component instance to the bean property. If the component tag refers to the property via its value attribute, then the component's value is bound to the property. If the component tag refers to the property via its binding attribute then the component itself is bound to the property.

What is virtual host
Multiple hosts plus domain names mapped to a single IP address.

What is W3C
World Wide Web Consortium. The international body that governs Internet standards. Its Web site is http://www.w3.org/.

What is WAR file
Web application archive file. A JAR archive that contains a Web module.

What is warning
A SAX parser warning is generated when the document's DTD contains duplicate definitions and in similar situations that are not necessarily an error but which the document author might like to know about, because they could be. See also fatal error, error.

What is Web application
An application written for the Internet, including those built with Java technologies such as JavaServer Pages and servlets, as well as those built with non-Java technologies such as CGI and Perl.

What is Web application, distributable
A Web application that uses J2EE technology written so that it can be deployed in a Web container distributed across multiple Java virtual machines running on the same host or different hosts. The deployment descriptor for such an application uses the distributable element.

What is Web component
A component that provides services in response to requests; either a servlet or a JSP page.
What is Web container
A container that implements the Web component contract of the J2EE architecture. This contract specifies a runtime environment for Web components that includes security, concurrency, life-cycle management, transaction, deployment, and other services. A Web container provides the same services as a JSP container as well as a federated view of the J2EE platform APIs. A Web container is provided by a Web or J2EE server.

What is Web container, distributed
A Web container that can run a Web application that is tagged as distributable and that executes across multiple Java virtual machines running on the same host or on different hosts.

What is Web container provider
A vendor that supplies a Web container.

What is Web module
A deployable unit that consists of one or more Web components, other resources, and a Web application deployment descriptor contained in a hierarchy of directories and files in a standard Web application format.

What is Web resource
A static or dynamic object contained in a Web application that can be referenced by a URL.

What is Web resource collection
A list of URL patterns and HTTP methods that describe a set of Web resources to be protected.

What is Web server
Software that provides services to access the Internet, an intranet, or an extranet. A Web server hosts Web sites, provides support for HTTP and other protocols, and executes server-side programs (such as CGI scripts or servlets) that perform certain functions. In the J2EE architecture, a Web server provides services to a Web container. For example, a Web container typically relies on a Web server to provide HTTP message handling. The J2EE architecture assumes that a Web container is hosted by a Web server from the same vendor, so it does not specify the contract between these two entities. A Web server can host one or more Web containers.
What is Web server provider
A vendor that supplies a Web server.

What is Web service
An application that exists in a distributed environment, such as the Internet. A Web service accepts a request, performs its function based on the request, and returns a response. The request and the response can be part of the same operation, or they can occur separately, in which case the consumer does not need to wait for a response. Both the request and the response usually take the form of XML, a portable data-interchange format, and are delivered over a wire protocol, such as HTTP.

What is well-formed
An XML document that is syntactically correct. It does not have any angle brackets that are not part of tags, all tags have an ending tag or are themselves self-ending, and all tags are fully nested. Knowing that a document is well formed makes it possible to process it. However, a well-formed document may not be valid. To determine that, you need a validating parser and a DTD.

What is Xalan
An interpreting version of XSLT.

What is XLink
The part of the XLL specification that is concerned with specifying links between documents.

What is XLL
The XML Link Language specification, consisting of XLink and XPointer.
What is XML
Extensible Markup Language. A markup language that allows you to define the tags (markup) needed to identify the content, data, and text in XML documents. It differs from HTML, the markup language most often used to present information on the Internet. HTML has fixed tags that deal mainly with style or presentation. An XML document must undergo a transformation into a language with style tags under the control of a style sheet before it can be presented by a browser or other presentation mechanism. Two types of style sheets used with XML are CSS and XSL. Typically, XML is transformed into HTML for presentation. Although tags can be defined as needed in the generation of an XML document, a document type definition (DTD) can be used to define the elements allowed in a particular type of document. A document can be compared by using the rules in the DTD to determine its validity and to locate particular elements in the document. A Web services application's J2EE deployment descriptors are expressed in XML with schemas defining allowed elements. Programs for processing XML documents use SAX or DOM APIs.

What is XML registry
See registry.

What is XML Schema
The W3C specification for defining the structure, content, and semantics of XML documents.

What is XPath
An addressing mechanism for identifying the parts of an XML document.

What is XPointer
The part of the XLL specification that is concerned with identifying sections of documents so that they can be referenced in links or included in other documents. What is XSL
Extensible Stylesheet Language. A standard that lets you do the following:
Specify an addressing mechanism, so that you can identify the parts of an XML document that a transformation applies to (XPath).
Specify tag conversions, so that you can convert XML data into different formats (XSLT).
Specify display characteristics, such page sizes, margins, and font heights and widths, as well as the flow objects on each page. Information fills in one area of a page and then automatically flows to the next object when that area fills up. That allows you to wrap text around pictures, for example, or to continue a newsletter article on a different page (XSL-FO).

What is XSL-FO
A subcomponent of XSL used for describing font sizes, page layouts, and how information flows from one page to another.

What is XSLT
XSL Transformations. An XML document that controls the transformation of an XML document into another XML document or HTML. The target document often has presentation-related tags dictating how it will be rendered by a browser or other presentation mechanism. XSLT was formerly a part of XSL, which also included a tag language of style flow objects.

What is XSLTC
A compiling version of XSLT

J2EE QUESTIONS1

2009-04-30T06:09:00.000-07:00

What makes J2EE suitable for distributed multitiered Applications?
- The J2EE platform uses a multitiered distributed application model. Application logic is divided into components according to function, and the various application components that make up a J2EE application are installed on different machines depending on the tier in the multitiered J2EE environment to which the application component belongs. The J2EE application parts are:

Client-tier components run on the client machine.
Web-tier components run on the J2EE server.
Business-tier components run on the J2EE server.
Enterprise information system (EIS)-tier software runs on the EIS server.

What is J2EE?
- J2EE is an environment for developing and deploying enterprise applications. The J2EE platform consists of a set of services, application programming interfaces (APIs), and protocols that provide the functionality for developing multitiered, web-based applications.

What are the components of J2EE application?
- A J2EE component is a self-contained functional software unit that is assembled into a J2EE application with its related classes and files and communicates with other components. The J2EE specification defines the following J2EE components:

Application clients and applets are client components.
Java Servlet and JavaServer Pages technology components are web components.
Enterprise JavaBeans components (enterprise beans) are business components.
Resource adapter components provided by EIS and tool vendors.

What do Enterprise JavaBeans components contain?
- Enterprise JavaBeans components contains Business code, which is logic
that solves or meets the needs of a particular business domain such as banking, retail, or finance, is handled by enterprise beans running in the business tier. All the business code is contained inside an Enterprise Bean which receives data from client programs, processes it (if necessary), and sends it to the enterprise information system tier for storage. An enterprise bean also retrieves data from storage, processes it (if necessary), and sends it back to the client program.

Is J2EE application only a web-based?
- No, It depends on type of application that client wants. A J2EE application can be web-based or non-web-based. if an application client executes on the client machine, it is a non-web-based J2EE application. The J2EE application can provide a way for users to handle tasks such as J2EE system or application administration. It typically has a graphical user interface created from Swing or AWT APIs, or a command-line interface. When user request, it can open an HTTP connection to establish communication with a servlet running in the web tier.

Are JavaBeans J2EE components?
- No. JavaBeans components are not considered J2EE components by the J2EE specification. They are written to manage the data flow between an application client or applet and components running on the J2EE server or between server components and a database. JavaBeans components written for the J2EE platform have instance variables and get and set methods for accessing the data in the instance variables. JavaBeans components used in this way are typically simple in design and implementation, but should conform to the naming and design conventions outlined in the JavaBeans component architecture.

Is HTML page a web component?
- No. Static HTML pages and applets are bundled with web components during application assembly, but are not considered web components by the J2EE specification. Even the server-side utility classes are not considered web components, either.

What can be considered as a web component?
- J2EE Web components can be either servlets or JSP pages. Servlets are Java programming language classes that dynamically process requests and construct responses. JSP pages are text-based documents that execute as servlets but allow a more natural approach to creating static content.

What is the container?
- Containers are the interface between a component and the low-level platform specific functionality that supports the component. Before a Web, enterprise bean, or application client component can be executed, it must be assembled into a J2EE application and deployed into its container.

What are container services?
- A container is a runtime support of a system-level entity. Containers provide components with services such as lifecycle management, security, deployment, and threading.

What is the web container?
- Servlet and JSP containers are collectively referred to as Web containers. It manages the execution of JSP page and servlet components for J2EE applications. Web components and their container run on the J2EE server.

What is Enterprise JavaBeans (EJB) container?
- It manages the execution of enterprise beans for J2EE applications.
Enterprise beans and their container run on the J2EE server.

What is Applet container?
- IManages the execution of applets. Consists of a Web browser and Java Plugin running on the client together.

How do we package J2EE components?
- J2EE components are packaged separately and bundled into a J2EE application for deployment. Each component, its related files such as GIF and HTML files or server-side utility classes, and a deployment descriptor are assembled into a module and added to the J2EE application. A J2EE application is composed of one or more enterprise bean,Web, or application client component modules. The final enterprise solution can use one J2EE application or be made up of two or more J2EE applications, depending on design requirements. A J2EE application and each of its modules has its own deployment descriptor. A deployment descriptor is an XML document with an .xml extension that describes a component’s deployment settings.

What is a thin client?
- A thin client is a lightweight interface to the application that does not have such operations like query databases, execute complex business rules, or connect to legacy applications.

What are types of J2EE clients?
- Following are the types of J2EE clients:
Applets
Application clients
Java Web Start-enabled rich clients, powered by Java Web Start technology.
Wireless clients, based on Mobile Information Device Profile (MIDP) technology.

What is deployment descriptor?
- A deployment descriptor is an Extensible Markup
Language (XML) text-based file with an .xml extension that describes a component’s deployment settings. A J2EE application and each of its modules has its own deployment descriptor. For example, an enterprise bean module deployment descriptor declares transaction attributes and security authorizations
for an enterprise bean. Because deployment descriptor information is declarative, it can be changed without modifying the bean source code. At run time, the J2EE server reads the deployment descriptor and acts upon the component accordingly.

What is the EAR file?
- An EAR file is a standard JAR file with an .ear extension, named from Enterprise ARchive file. A J2EE application with all of its modules is delivered in EAR file.

What is JTA and JTS?
- JTA is the abbreviation for the Java Transaction API. JTS is the abbreviation for the Jave Transaction Service. JTA provides a standard interface and allows you to demarcate transactions in a manner that is independent of the transaction manager implementation. The J2EE SDK implements the transaction manager with JTS. But your code doesn’t call the JTS methods directly. Instead, it invokes the JTA methods, which then call the lower-level JTS routines. Therefore, JTA is a high level transaction interface that your application uses to control transaction. and JTS is a low level transaction interface and ejb uses behind the scenes (client code doesn’t directly interact with JTS. It is based on object transaction service(OTS) which is part of CORBA.

What is JAXP?
- JAXP stands for Java API for XML. XML is a language for representing and describing text-based data which can be read and handled by any program or tool that uses XML APIs. It provides standard services to determine the type of an arbitrary piece of data, encapsulate access to it, discover the operations available on it, and create the appropriate JavaBeans component to perform those operations.

What is J2EE Connector?
- The J2EE Connector API is used by J2EE tools vendors and system integrators to create resource adapters that support access to enterprise information systems that can be plugged into any J2EE product. Each type of database or EIS has a different resource adapter. Note: A resource adapter is a software component that allows J2EE application components to access and interact with the underlying resource manager. Because a resource adapter is specific to its resource manager, there is typically a different resource adapter for each type of database or enterprise information system.

What is JAAP?
- The Java Authentication and Authorization Service (JAAS) provides a way for a J2EE application to authenticate and authorize a specific user or group of users to run it. It is a standard Pluggable Authentication Module (PAM) framework that extends the Java 2 platform security architecture to support user-based authorization.

What is Java Naming and Directory Service?
- The JNDI provides naming and directory functionality. It provides applications with methods for performing standard directory operations, such as associating attributes with objects and searching for objects using their attributes. Using JNDI, a J2EE application can store and retrieve any type of named Java object. Because JNDI is independent of any specific implementations, applications can use JNDI to access multiple naming and directory services, including existing naming and
directory services such as LDAP, NDS, DNS, and NIS.

What is Struts?
- A Web page development framework. Struts combines Java Servlets, Java Server Pages, custom tags, and message resources into a unified framework. It is a cooperative, synergistic platform, suitable for development teams, independent developers, and everyone between.

How is the MVC design pattern used in Struts framework?
- In the MVC design pattern, application flow is mediated by a central Controller. The Controller delegates requests to an appropriate handler. The handlers are tied to a Model, and each handler acts as an adapter between the request and the Model. The Model represents, or encapsulates, an application’s business logic or state. Control is usually then forwarded back through the Controller to the appropriate View. The forwarding can be determined by consulting a set of mappings, usually loaded from a database or configuration file. This provides a loose coupling between the View and Model, which can make an application significantly easier to create and maintain. Controller: Servlet controller which supplied by Struts itself; View: what you can see on the screen, a JSP page and presentation components; Model: System state and a business logic JavaBeans.

module4

2009-04-05T02:26:00.000-07:00

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1. What is a transient variable?
A transient variable is a variable that may not be serialized.

2. Which containers use a border Layout as their default layout?
The window, Frame and Dialog classes use a border layout as their default layout.

3. Why do threads block on I/O?
Threads block on I/O (that is enters the waiting state) so that other threads may execute while the I/O Operation is performed.

4. How are Observer and Observable used?
Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.

5. What is synchronization and why is it important?
With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often leads to significant errors.

6. Can a lock be acquired on a class?
Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object.

7. What's new with the stop(), suspend() and resume() methods in JDK 1.2?
The stop(), suspend() and resume() methods have been deprecated in JDK 1.2.

8. Is null a keyword?
The null value is not a keyword.

9. What is the preferred size of a component?
The preferred size of a component is the minimum component size that will allow the component to display normally.

10. What method is used to specify a container's layout?
The setLayout() method is used to specify a container's layout.

11. Which containers use a FlowLayout as their default layout?
The Panel and Applet classes use the FlowLayout as their default layout.

12. What state does a thread enter when it terminates its processing?
When a thread terminates its processing, it enters the dead state.

13. What is the Collections API?
The Collections API is a set of classes and interfaces that support operations on collections of objects.

14. which characters may be used as the second character of an identifier, but not as the first character of an identifier?
The digits 0 through 9 may not be used as the first character of an identifier but they may be used after the first character of an identifier.

15. What is the List interface?
The List interface provides support for ordered collections of objects.

16. How does Java handle integer overflows and underflows?

It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.

17. What is the Vector class?
The Vector class provides the capability to implement a growable array of objects

18. What modifiers may be used with an inner class that is a member of an outer class?
A (non-local) inner class may be declared as public, protected, private, static, final, or abstract.

19. What is an Iterator interface?
The Iterator interface is used to step through the elements of a Collection.

20. What is the difference between the >> and >>> operators?
The >> operator carries the sign bit when shifting right. The >>> zero-fills bits that have been shifted out.

21. Which method of the Component class is used to set the position and size of a component?
setBounds()

22. How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?
Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns.

23 What is the difference between yielding and sleeping?
When a task invokes its yield() method, it returns to the ready state. When a task invokes its sleep() method, it returns to the waiting state.

24. Which java.util classes and interfaces support event handling?
The EventObject class and the EventListener interface support event processing.

25. Is sizeof a keyword?
The sizeof operator is not a keyword.

26. What are wrapper classes?
Wrapper classes are classes that allow primitive types to be accessed as objects.

27. Does garbage collection guarantee that a program will not run out of memory?
Garbage collection does not guarantee that a program will not run out of memory. It is possible for programs to use up memory resources faster than they are garbage collected. It is also possible for programs to create objects that are not subject to garbage collection.

28. What restrictions are placed on the location of a package statement within a source code file?
A package statement must appear as the first line in a source code file (excluding blank lines and comments).

29. Can an object's finalize() method be invoked while it is reachable?
An object's finalize() method cannot be invoked by the garbage collector while the object is still reachable. However, an object's finalize() method may be invoked by other objects.

30. What is the immediate superclass of the Applet class?
Panel

31. What is the difference between preemptive scheduling and time slicing?
Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then reenters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors.

32. Name three Component subclasses that support painting.
The Canvas, Frame, Panel, and Applet classes support painting.

33. What value does readLine() return when it has reached the end of a file?
The readLine() method returns null when it has reached the end of a file.

34. What is the immediate superclass of the Dialog class?
Window.

35. What is clipping?
Clipping is the process of confining paint operations to a limited area or shape.

36. What is a native method?
A native method is a method that is implemented in a language other than Java.

37. Can a for statement loop indefinitely?
Yes, a for statement can loop indefinitely. For example, consider the following:
for(;;) ;

38. What are order of precedence and associativity, and how are they used?
Order of precedence determines the order in which operators are evaluated in expressions. Associatity determines whether an expression is evaluated left-to-right or right-to-left

39. When a thread blocks on I/O, what state does it enter?
A thread enters the waiting state when it blocks on I/O.

40. To what value is a variable of the String type automatically initialized?
The default value of a String type is null.

41. What is the catch or declare rule for method declarations?
If a checked exception may be thrown within the body of a method, the method must either catch the exception or declare it in its throws clause.

42. What is the difference between a MenuItem and a CheckboxMenuItem?
The CheckboxMenuItem class extends the MenuItem class to support a menu item that may be checked or unchecked.

43. What is a task's priority and how is it used in scheduling?
A task's priority is an integer value that identifies the relative order in which it should be executed with respect to other tasks. The scheduler attempts to schedule higher priority tasks before lower priority tasks.

44. What class is the top of the AWT event hierarchy?
The java.awt.AWTEvent class is the highest-level class in the AWT event-class hierarchy.

45. When a thread is created and started, what is its initial state?
A thread is in the ready state after it has been created and started.

46. Can an anonymous class be declared as implementing an interface and extending a class?
An anonymous class may implement an interface or extend a superclass, but may not be declared to do both.

47. What is the range of the short type?
The range of the short type is -(2^15) to 2^15 - 1.

48. What is the range of the char type?
The range of the char type is 0 to 2^16 - 1.

49. In which package are most of the AWT events that support the event-delegation model defined?
Most of the AWT-related events of the event-delegation model are defined in the java.awt.event package. The AWTEvent class is defined in the java.awt package.

50. What is the immediate superclass of Menu?
MenuItem

51. What is the purpose of finalization?
The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.

52. Which class is the immediate superclass of the MenuComponent class.
Object

53. What invokes a thread's run() method?
After a thread is started, via its start() method or that of the Thread class, the JVM invokes the thread's run() method when the thread is initially executed.

54. What is the difference between the Boolean & operator and the && operator?
If an expression involving the Boolean & operator is evaluated, both operands are evaluated. Then the & operator is applied to the operand. When an expression involving the && operator is evaluated, the first operand is evaluated. If the first operand returns a value of true then the second operand is evaluated. The && operator is then applied to the first and second operands. If the first operand evaluates to false, the evaluation of the second operand is skipped.

55. Name three subclasses of the Component class.
Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, or TextComponent

56. What is the GregorianCalendar class?
The GregorianCalendar provides support for traditional Western calendars.

57. Which Container method is used to cause a container to be laid out and redisplayed?
validate()

58. What is the purpose of the Runtime class?
The purpose of the Runtime class is to provide access to the Java runtime system.

59. How many times may an object's finalize() method be invoked by the
garbage collector?
An object's finalize() method may only be invoked once by the garbage collector.

60. What is the purpose of the finally clause of a try-catch-finally statement?
The finally clause is used to provide the capability to execute code no matter whether or not an exception is thrown or caught.

61. What is the argument type of a program's main() method?
A program's main() method takes an argument of the String[] type.

62. Which Java operator is right associative?
The = operator is right associative.

63. What is the Locale class?
The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.64. Can a double value be cast to a byte?
Yes, a double value can be cast to a byte.

65. What is the difference between a break statement and a continue statement?
A break statement results in the termination of the statement to which it applies (switch, for, do, or while). A continue statement is used to end the current loop iteration and return control to the loop statement.

66. What must a class do to implement an interface?
It must provide all of the methods in the interface and identify the interface in its implements clause.

67. What method is invoked to cause an object to begin executing as a separate thread?
The start() method of the Thread class is invoked to cause an object to begin executing as a separate thread.

68. Name two subclasses of the TextComponent class.
TextField and TextArea

69. What is the advantage of the event-delegation model over the earlier event-inheritance model?
The event-delegation model has two advantages over the event-inheritance model. First, it enables event handling to be handled by objects other than the ones that generate the events (or their containers). This allows a clean separation between a component's design and its use. The other advantage of the event-delegation model is that it performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to repeatedly process unhandled events, as is the case of the event-inheritance
model.

70. Which containers may have a MenuBar?
Frame

71. How are commas used in the initialization and iteration parts of a for statement?
Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.

72. What is the purpose of the wait(), notify(), and notifyAll() methods?
The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods.

73. What is an abstract method?
An abstract method is a method whose implementation is deferred to a subclass.

74. How are Java source code files named?
A Java source code file takes the name of a public class or interface that is defined within the file. A source code file may contain at most one public class or interface. If a public class or interface is defined within a source code file, then the source code file must take the name of the public class or interface. If no public class or interface is defined within a source code file, then the file must take on a name that is different than its classes and interfaces. Source code files use the .java extension.

75. What is the relationship between the Canvas class and the Graphics class?
A Canvas object provides access to a Graphics object via its paint() method.

76. What are the high-level thread states?
The high-level thread states are ready, running, waiting, and dead.

77. What value does read() return when it has reached the end of a file?
The read() method returns -1 when it has reached the end of a file.
78. Can a Byte object be cast to a double value?
No, an object cannot be cast to a primitive value.

79. What is the difference between a static and a non-static inner class?
A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances.

80. What is the difference between the String and StringBuffer classes?
String objects are constants. StringBuffer objects are not.

81. If a variable is declared as private, where may the variable be accessed?
A private variable may only be accessed within the class in which it is declared.

82. What is an object's lock and which objects have locks?
An object's lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object's lock. All objects and classes have locks. A class's lock is acquired on the class's Class object.

83. What is the Dictionary class?
The Dictionary class provides the capability to store key-value pairs.

84. How are the elements of a BorderLayout organized?
The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.

85. What is the % operator?
It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.

86. When can an object reference be cast to an interface reference?
An object reference be cast to an interface reference when the object implements the referenced interface.

87. What is the difference between a Window and a Frame?
The Frame class extends Window to define a main application window that can have a menu bar.

88. Which class is extended by all other classes?
The Object class is extended by all other classes.

89. Can an object be garbage collected while it is still reachable?
A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected..

90. Is the ternary operator written x : y ? z or x ? y : z ?
It is written x ? y : z.

91. What is the difference between the Font and FontMetrics classes?
The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.

92. How is rounding performed under integer division?
The fractional part of the result is truncated. This is known as rounding toward zero.

93. What happens when a thread cannot acquire a lock on an object?
If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object's lock, it enters the waiting state until the lock becomes available.

94. What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?
The Reader/Writer class hierarchy is character-oriented, and the InputStream/OutputStream class hierarchy is byte-oriented.

95. What classes of exceptions may be caught by a catch clause?
A catch clause can catch any exception that may be assigned to the Throwable type. This includes the Error and Exception types.

96. If a class is declared without any access modifiers, where may the class be accessed?
A class that is declared without any access modifiers is said to have package access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.

97. What is the SimpleTimeZone class?
The SimpleTimeZone class provides support for a Gregorian calendar.

98. What is the Map interface?
The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.99. Does a class inherit the constructors of its superclass?
A class does not inherit constructors from any of its super classes.

100. For which statements does it make sense to use a label?
The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement.

101. What is the purpose of the System class?
The purpose of the System class is to provide access to system resources.

102. Which TextComponent method is used to set a TextComponent to the read-only state?
setEditable()

103. How are the elements of a CardLayout organized?
The elements of a CardLayout are stacked, one on top of the other, like a deck of cards.

104. Is &&= a valid Java operator?
No, it is not.

105. Name the eight primitive Java types.
The eight primitive types are byte, char, short, int, long, float, double, and boolean.
106. Which class should you use to obtain design information about an object?
The Class class is used to obtain information about an object's design.

107. What is the relationship between clipping and repainting?
When a window is repainted by the AWT painting thread, it sets the clipping regions to the area of the window that requires repainting.

108. Is "abc" a primitive value?
The String literal "abc" is not a primitive value. It is a String object.

109. What is the relationship between an event-listener interface and an event-adapter class?
An event-listener interface defines the methods that must be implemented by an event handler for a particular kind of event. An event adapter provides a default implementation of an event-listener interface.

110. What restrictions are placed on the values of each case of a switch statement?
During compilation, the values of each case of a switch statement must evaluate to a value that can be promoted to an int value.

111. What modifiers may be used with an interface declaration?
An interface may be declared as public or abstract.

112. Is a class a subclass of itself?
A class is a subclass of itself.

113. What is the highest-level event class of the event-delegation model?
The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.

114. What event results from the clicking of a button?
The ActionEvent event is generated as the result of the clicking of a button.

115. How can a GUI component handle its own events?
A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener.

116. What is the difference between a while statement and a do statement?
A while statement checks at the beginning of a loop to see whether the next loop iteration should occur. A do statement checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the body of a loop at least once.

117. How are the elements of a GridBagLayout organized?
The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.

118. What advantage do Java's layout managers provide over traditional windowing systems?
Java uses layout managers to lay out components in a consistent manner across all windowing platforms. Since Java's layout managers aren't tied to absolute sizing and positioning, they are able to accommodate platform-specific differences among windowing systems.

119. What is the Collection interface?
The Collection interface provides support for the implementation of a mathematical bag - an unordered collection of objects that may contain duplicates.

120. What modifiers can be used with a local inner class?
A local inner class may be final or abstract.

121. What is the difference between static and non-static variables?
A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.

122. What is the difference between the paint() and repaint() methods?
The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.

123. What is the purpose of the File class?
The File class is used to create objects that provide access to the files and directories of a local file system.

124. Can an exception be rethrown?
Yes, an exception can be rethrown.

125. Which Math method is used to calculate the absolute value of a number?
The abs() method is used to calculate absolute values.

126. How does multithreading take place on a computer with a single CPU?
The operating system's task scheduler allocates execution time to multiple tasks. By quickly switching between executing tasks, it creates the impression that tasks execute sequentially.

127. When does the compiler supply a default constructor for a class?
The compiler supplies a default constructor for a class if no other constructors are provided.

128. When is the finally clause of a try-catch-finally statement executed?
The finally clause of the try-catch-finally statement is always executed unless the thread of execution terminates or an exception occurs within the execution of the finally clause.

129. Which class is the immediate superclass of the Container class?
Component

130. If a method is declared as protected, where may the method be accessed?
A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.

131. How can the Checkbox class be used to create a radio button?
By associating Checkbox objects with a CheckboxGroup.

132. Which non-Unicode letter characters may be used as the first character of an identifier?
The non-Unicode letter characters $ and _ may appear as the first character of an identifier

133. What restrictions are placed on method overloading?
Two methods may not have the same name and argument list but different return types.

134. What happens when you invoke a thread's interrupt method while it is sleeping or waiting?
When a task's interrupt() method is executed, the task enters the ready state. The next time the task enters the running state, an InterruptedException is thrown.

135. What is casting?
There are two types of casting, casting between primitive numeric types and casting between object references. Casting between numeric types is used to convert larger values, such as double values, to smaller values, such as byte values. Casting between object references is used to refer to an object by a compatible class, interface, or array type reference.

136. What is the return type of a program's main() method?
A program's main() method has a void return type.

137. Name four Container classes.
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane

138. What is the difference between a Choice and a List?
A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices. Only one item may be selected from a Choice. A List may be displayed in such a way that several List items are visible. A List supports the selection of one or more List items.

139. What class of exceptions are generated by the Java run-time system?
The Java runtime system generates RuntimeException and Error exceptions.

140. What class allows you to read objects directly from a stream?
The ObjectInputStream class supports the reading of objects from input streams.

141. What is the difference between a field variable and a local variable?
A field variable is a variable that is declared as a member of a class. A local variable is a variable that is declared local to a method.

142. Under what conditions is an object's finalize() method invoked by the garbage collector?
The garbage collector invokes an object's finalize() method when it detects that the object has become unreachable.

143. How are this () and super () used with constructors?
this() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor.

144. What is the relationship between a method's throws clause and the exceptions that can be thrown during the method's execution?
A method's throws clause must declare any checked exceptions that are not caught within the body of the method.

145. What is the difference between the JDK 1.02 event model and the event-delegation model introduced with JDK 1.1?
The JDK 1.02 event model uses an event inheritance or bubbling approach. In this model, components are required to handle their own events. If they do not handle a particular event, the event is inherited by (or bubbled up to) the component's container. The container then either handles the event or it is bubbled up to its container and so on, until the highest-level container has been tried.
In the event-delegation model, specific objects are designated as event handlers for GUI components. These objects implement event-listener interfaces. The event-delegation model is more efficient than the event-inheritance model because it eliminates the processing required to support the bubbling of unhandled events.

146. How is it possible for two String objects with identical values not to be equal under the == operator?
The == operator compares two objects to determine if they are the same object in memory. It is possible for two String objects to have the same value, but located indifferent areas of memory.

147. Why are the methods of the Math class static?
So they can be invoked as if they are a mathematical code library.

148. What Checkbox method allows you to tell if a Checkbox is checked?
getState()

149. What state is a thread in when it is executing?
An executing thread is in the running state.

150. What are the legal operands of the instanceof operator?
The left operand is an object reference or null value and the right operand is a class, interface, or array type.

151. How are the elements of a GridLayout organized?
The elements of a GridBad layout are of equal size and are laid out using the squares of a grid.

152. What an I/O filter?
An I/O filter is an object that reads from one stream and writes to another, usually altering the data in some way as it is passed from one stream to another.

153. If an object is garbage collected, can it become reachable again?
Once an object is garbage collected, it ceases to exist. It can no longer become reachable again.

154. What is the Set interface?
The Set interface provides methods for accessing the elements of a finite mathematical set. Sets do not allow duplicate elements.

155. What classes of exceptions may be thrown by a throw statement?
A throw statement may throw any expression that may be assigned to the Throwable type.

156. What are E and PI?
E is the base of the natural logarithm and PI is mathematical value pi.

157. Are true and false keywords?
The values true and false are not keywords.

158. What is a void return type?
A void return type indicates that a method does not return a value.

159. What is the purpose of the enableEvents() method?
The enableEvents() method is used to enable an event for a particular object. Normally, an event is enabled when a listener is added to an object for a particular event. The enableEvents() method is used by objects that handle events by overriding their event-dispatch methods.

160. What is the difference between the File and RandomAccessFile classes?
The File class encapsulates the files and directories of the local file system. The RandomAccessFile class provides the methods needed to directly access data contained in any part of a file.

161. What happens when you add a double value to a String?
The result is a String object.162. What is your platform's default character encoding?
If you are running Java on English Windows platforms, it is probably Cp1252. If you are running Java on English Solaris platforms, it is most likely 8859_1..

163. Which package is always imported by default?
The java.lang package is always imported by default.

164. What interface must an object implement before it can be written to a stream as an object?
An object must implement the Serializable or Externalizable interface before it can be written to a stream as an object.

165. How are this and super used?
this is used to refer to the current object instance. super is used to refer to the variables and methods of the superclass of the current object instance.

166. What is the purpose of garbage collection?
The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources may be reclaimed and
reused.

167. What is a compilation unit?
A compilation unit is a Java source code file.

168. What interface is extended by AWT event listeners?
All AWT event listeners extend the java.util.EventListener interface.

169. What restrictions are placed on method overriding?
Overridden methods must have the same name, argument list, and return type.
The overriding method may not limit the access of the method it overrides.
The overriding method may not throw any exceptions that may not be thrown
by the overridden method.

170. How can a dead thread be restarted?
A dead thread cannot be restarted.

171. What happens if an exception is not caught?
An uncaught exception results in the uncaughtException() method of the thread's ThreadGroup being invoked, which eventually results in the termination of the program in which it is thrown.

172. What is a layout manager?
A layout manager is an object that is used to organize components in a container.

173. Which arithmetic operations can result in the throwing of an ArithmeticException?
Integer / and % can result in the throwing of an ArithmeticException.

174. What are three ways in which a thread can enter the waiting state?
A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object's lock, or by invoking an object's wait() method. It can also enter the waiting state by invoking its
(deprecated) suspend() method.

175. Can an abstract class be final?
An abstract class may not be declared as final.176. What is the ResourceBundle class?
The ResourceBundle class is used to store locale-specific resources that can be loaded by a program to tailor the program's appearance to the particular locale in which it is being run.

177. What happens if a try-catch-finally statement does not have a catch clause to handle an exception that is thrown within the body of the try statement?
The exception propagates up to the next higher level try-catch statement (if any) or results in the program's termination.

178. What is numeric promotion?
Numeric promotion is the conversion of a smaller numeric type to a larger numeric type, so that integer and floating-point operations may take place. In numerical promotion, byte, char, and short values are converted to int
values. The int values are also converted to long values, if necessary. The long and float values are converted to double values, as required.

179. What is the difference between a Scrollbar and a ScrollPane?
A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. A ScrollPane handles its own events and performs its own scrolling.

180. What is the difference between a public and a non-public class?
A public class may be accessed outside of its package. A non-public class may not be accessed outside of its package.

181. To what value is a variable of the boolean type automatically initialized?
The default value of the boolean type is false.

182. Can try statements be nested?
Try statements may be tested.

183. What is the difference between the prefix and postfix forms of the ++ operator?
The prefix form performs the increment operation and returns the value of the increment operation. The postfix form returns the current value all of the expression and then performs the increment operation on that value.

184. What is the purpose of a statement block?
A statement block is used to organize a sequence of statements as a single statement group.

185. What is a Java package and how is it used?
A Java package is a naming context for classes and interfaces. A package is used to create a separate name space for groups of classes and interfaces. Packages are also used to organize related classes and interfaces into a single API unit and to control accessibility to these classes and interfaces.

186. What modifiers may be used with a top-level class?
A top-level class may be public, abstract, or final.

187. What are the Object and Class classes used for?
The Object class is the highest-level class in the Java class hierarchy. The Class class is used to represent the classes and interfaces that are loaded by a Java program.

188. How does a try statement determine which catch clause should be used to handle an exception?
When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exception is executed.
The remaining catch clauses are ignored.

189. Can an unreachable object become reachable again?
An unreachable object may become reachable again. This can happen when the object's finalize() method is invoked and the object performs an operation which causes it to become accessible to reachable objects.190. When is an object subject to garbage collection?
An object is subject to garbage collection when it becomes unreachable to the program in which it is used.

191. What method must be implemented by all threads?
All tasks must implement the run() method, whether they are a subclass of Thread or implement the Runnable interface.

192. What methods are used to get and set the text label displayed by a Button object?
getLabel() and setLabel()

193. Which Component subclass is used for drawing and painting?
Canvas

194. What are synchronized methods and synchronized statements?
Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement195. What are the two basic ways in which classes that can be run as threads may be defined?
A thread class may be declared as a subclass of Thread, or it may implement the Runnable interface.

196. What are the problems faced by Java programmers who don't use layout managers?
Without layout managers, Java programmers are faced with determining how their GUI will be displayed across multiple windowing systems and finding a common sizing and positioning that will work within the constraints imposed by each windowing system.

197. What is the difference between an if statement and a switch statement?
The if statement is used to select among two alternatives. It uses a boolean expression to decide which alternative should be executed. The switch statement is used to select among multiple alternatives. It uses an int expression to determine which alternative should be executed.

module3

2009-04-05T02:08:00.001-07:00

1) Explain Java Collections Framework?

     Java Collections Framework provides a well designed set of interfaces and classes that support operations on a collection of objects.

2) Explain Iterator Interface.

     An Iterator is similar to the Enumeration interface. With the Iterator interface methods, you can traverse a collection from start to end and safely remove elements from the underlying collection. The iterator() method generally used in query operations.

Basic methods:

iterator.remove();

iterator.hasNext();

iterator.next();

3) Explain Enumeration Interface.

     The Enumeration interface allows you to iterate through all the elements of a collection. Iterating through an Enumeration is similar to iterating through an Iterator. However, there is no removal support with Enumeration.

Basic methods:

boolean hasMoreElements();

Object nextElement();

4) What is the difference between Enumeration and Iterator interface?

     The Enumeration interface allows you to iterate through all the elements of a collection. Iterating through an Enumeration is similar to iterating through an Iterator. However, there is no removal support with Enumeration.

5) Explain Set Interface.

     In mathematical concept, a set is just a group of unique items, in the sense that the group contains no duplicates. The Set interface extends the Collection interface. Set does not allow duplicates in the collection. In Set implementations null is valid entry, but allowed only once.

6) What are the two types of Set implementations available in the Collections Framework?

     HashSet and TreeSet are the two Set implementations available in the Collections Framework.

7) What is the difference between HashSet and TreeSet?

     HashSet Class implements java.util.Set interface to eliminate the duplicate entries and uses hashing for storage. Hashing is nothing but mapping between a key value and a data item, this provides efficient searching.

The TreeSet Class implements java.util.Set interface provides an ordered set, eliminates duplicate entries and uses tree for storage.

8) What is a List?

     List is an ordered and non duplicated collection of objects. The List interface extends the Collection interface.

9) What are the two types of List implementations available in the Collections Framework?

     ArrayList and LinkedList are the two List implementations available in the Collections Framework.

10) What is the difference between ArrayList and LinkedList?

     The ArrayList Class implements java.util.List interface and uses array for storage. An array storage's are generally faster but we cannot insert and delete entries in middle of the list. To achieve this kind of addition and deletion requires a new array constructed. You can access any element at randomly.

The LinkedList Class implements java.util.List interface and uses linked list for storage. A linked list allow elements to be added, removed from the collection at any location in the container by ordering the elements. With this implementation you can only access the elements in sequentially.

11) What collection will you use to implement a queue?

     LinkedList

12) Explain Map Interface.

     A map is a special kind of set with no duplicates. The key values are used to lookup, or index the stored data. The Map interface is not an extension of Collection interface, it has it's own hierarchy. Map does not allow duplicates in the collection. In Map implementations null is valid entry, but allowed only once.

13) What are the two types of Map implementations available in the Collections Framework?

     HashMap and TreeMap are two types of Map implementations available in the Collections Framework.

14) What is the difference between HashMap and TreeMap?

     The HashMap Class implements java.util.Map interface and uses hashing for storage. Indirectly Map uses Set functionality so, it does not permit duplicates. The TreeMap Class implements java.util.Map interface and uses tree for storage. It provides the ordered map.

15) Explain the functionality of Vector Class?

     Once array size is set you cannot change size of the array.
To deal with this kind of situations we use Vector. Vector grows and shrink it's size automatically. Vector allows to store only objects not primitives. To store primitives, convert primitives in to objects using wrapper classes before adding them into Vector. The Vector reallocates and resizes itself automatically.

16) What does the following statement convey?

Vector vt = new Vector(3, 10);

     vt is an instance of Vector class with an initial capacity of 3 and grows in increment of 10 in each relocation

17) How do you store a primitive data type within a Vector or other collections class?

     You need to wrap the primitive data type into one of the wrapper classes found in the java.lang package, like Integer, Float, or Double, as in:

Integer in = new Integer(5);

18) What is the difference between Vector and ArrayList?

     Vector and ArrayList are very similar. Both of them represent a growable array. The main difference is that Vector is synchronized while ArrayList is not.

19) What is the difference between Hashtable and HashMap?

     Both provide key-value access to data. The key differences are :

a. Hashtable is synchronised but HasMap is not synchronised.

b. HashMap permits null values but Hashtable doesn't allow null values.

c. iterator in the HashMap is fail-safe while the enumerator for the Hashtable is not fail safe.

20) How do I make an array larger?

     You cannot directly make an array larger. You must make a new (larger) array and copy the original elements into it, usually with System.arraycopy(). If you find yourself frequently doing this, the Vector class does this automatically for you, as long as your arrays are not of primitive data types.

21) Which is faster, synchronizing a HashMap or using a Hashtable for thread-safe access?

     Because a synchronized HashMap requires an extra method call, a Hashtable is faster for synchronized access.

22) In which package would you find the interfaces and classes defined in the Java Collection Framework?

     java.util

23) Which method in the System class allows you to copy elements from one array to another?

     System.arraycopy()

24) When using the System.arraycopy() method, What exception is thrown if the destination array is smaller than the source array?

     ArrayIndexOutofBoundsException

25) What is the use of Locale class?

     The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region

26) What is the use of GregorianCalendar class?

     The GregorianCalendar provides support for traditional Western calendars

27) What is the use of SimpleTimeZone class?

     The SimpleTimeZone class provides support for a Gregorian calendar

28) What is the use of ResourceBundle class?

     The ResourceBundle class is used to store locale-specific resources that can be loaded by a program to tailor the program's appearance to the particular locale in which it is being run.

module2

2009-04-04T22:41:00.001-07:00

What if the main method is declared as private?

The program compiles properly but at runtime it will give "Main method not public." message.

What is meant by pass by reference and pass by value in Java?

Pass by reference means, passing the address itself rather than passing the value. Pass by value means passing a copy of the value.

If you’re overriding the method equals() of an object, which other method you might also consider?

hashCode()

What is Byte Code?

Or

What gives java it’s “write once and run anywhere” nature?

All Java programs are compiled into class files that contain bytecodes. These byte codes can be run in any platform and hence java is said to be platform independent.

Expain the reason for each keyword of public static void main(String args[])?

public- main(..) is the first method called by java environment when a program is executed so it has to accessible from java environment. Hence the access specifier has to be public.

static: Java environment should be able to call this method without creating an instance of the class , so this method must be declared as static.

void: main does not return anything so the return type must be void

The argument String indicates the argument type which is given at the command line and arg is an array for string given during command line.

What is the Java API?

The Java API is a large collection of ready-made software components that provide many useful capabilities, such as graphical user interface (GUI) widgets.

What is the GregorianCalendar class?

The GregorianCalendar provides support for traditional Western calendars.

What is the ResourceBundle class?

The ResourceBundle class is used to store locale-specific resources that can be loaded by a program to tailor the program's appearance to the particular locale in which it is being run.

Why there are no global variables in Java?

Global variables are globally accessible. Java does not support globally accessible variables due to following reasons:

The global variables breaks the referential transparency

Global variables creates collisions in namespace.
How to convert String to Number in java program?

The valueOf() function of Integer class is is used to convert string to Number. Here is the code example:
String numString = "1000";
int id=Integer.valueOf(numString).intValue();

What is the SimpleTimeZone class?

The SimpleTimeZone class provides support for a Gregorian calendar.

What is the difference between a while statement and a do statement?

A while statement (pre test) checks at the beginning of a loop to see whether the next loop iteration should occur. A do while statement (post test) checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the loop body at least once.

What is the Locale class?

The Locale class is used to tailor a program output to the conventions of a particular geographic, political, or cultural region.

Describe the principles of OOPS.

There are three main principals of oops which are called Polymorphism, Inheritance and Encapsulation.

Explain the Inheritance principle.

Inheritance is the process by which one object acquires the properties of another object. Inheritance allows well-tested procedures to be reused and enables changes to make once and have effect in all relevant places

What is implicit casting?

Implicit casting is the process of simply assigning one entity to another without any transformation guidance to the compiler. This type of casting is not permitted in all kinds of transformations and may not work for all scenarios.

Example

int i = 1000;

long j = i; //Implicit casting

Is sizeof a keyword in java?

The sizeof operator is not a keyword.

What is a native method?

A native method is a method that is implemented in a language other than Java.

In System.out.println(), what is System, out and println?

System is a predefined final class, out is a PrintStream object and println is a built-in overloaded method in the out object.

What are Encapsulation, Inheritance and Polymorphism

Or

Explain the Polymorphism principle. Explain the different forms of Polymorphism.

Polymorphism in simple terms means one name many forms. Polymorphism enables one entity to be used as a general category for different types of actions. The specific action is determined by the exact nature of the situation.

Polymorphism exists in three distinct forms in Java:
• Method overloading
• Method overriding through inheritance
• Method overriding through the Java interface

What is explicit casting?

Explicit casting in the process in which the complier are specifically informed to about transforming the object.

Example

long i = 700.20;

int j = (int) i; //Explicit casting

What is the Java Virtual Machine (JVM)?

The Java Virtual Machine is software that can be ported onto various hardware-based platforms

What do you understand by downcasting?

The process of Downcasting refers to the casting from a general to a more specific type, i.e. casting down the hierarchy

What are Java Access Specifiers?

Or

What is the difference between public, private, protected and default Access Specifiers?

Or

What are different types of access modifiers?

Access specifiers are keywords that determine the type of access to the member of a class. These keywords are for allowing
privileges to parts of a program such as functions and variables. These are:
• Public : accessible to all classes
• Protected : accessible to the classes within the same package and any subclasses.
• Private : accessible only to the class to which they belong
• Default : accessible to the class to which they belong and to subclasses within the same package

Which class is the superclass of every class?

Object.

Name primitive Java types.

The 8 primitive types are byte, char, short, int, long, float, double, and boolean.

What is the difference between static and non-static variables?

Or

What are class variables?

Or

What is static in java?

Or

What is a static method?

A static variable is associated with the class as a whole rather than with specific instances of a class. Each object will share a common copy of the static variables i.e. there is only one copy per class, no matter how many objects are created from it. Class variables or static variables are declared with the static keyword in a class. These are declared outside a class and stored in static memory. Class variables are mostly used for constants. Static variables are always called by the class name. This variable is created when the program starts and gets destroyed when the programs stops. The scope of the class variable is same an instance variable. Its initial value is same as instance variable and gets a default value when its not initialized corresponding to the data type. Similarly, a static method is a method that belongs to the class rather than any object of the class and doesn't apply to an object or even require that any objects of the class have been instantiated.
Static methods are implicitly final, because overriding is done based on the type of the object, and static methods are attached to a class, not an object. A static method in a superclass can be shadowed by another static method in a subclass, as long as the original method was not declared final. However, you can't override a static method with a non-static method. In other words, you can't change a static method into an instance method in a subclass.

Non-static variables take on unique values with each object instance.

What is the difference between the boolean & operator and the && operator?

If an expression involving the boolean & operator is evaluated, both operands are evaluated, whereas the && operator is a short cut operator. When an expression involving the && operator is evaluated, the first operand is evaluated. If the first operand returns a value of true then the second operand is evaluated. If the first operand evaluates to false, the evaluation of the second operand is skipped.

How does Java handle integer overflows and underflows?

It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.

What if I write static public void instead of public static void?

Program compiles and runs properly.

What is the difference between declaring a variable and defining a variable?

In declaration we only mention the type of the variable and its name without initializing it. Defining means declaration + initialization. E.g. String s; is just a declaration while String s = new String ("bob"); Or String s = "bob"; are both definitions.

What type of parameter passing does Java support?

In Java the arguments (primitives and objects) are always passed by value. With objects, the object reference itself is passed by value and so both the original reference and parameter copy both refer to the same object.

Explain the Encapsulation principle.

Encapsulation is a process of binding or wrapping the data and the codes that operates on the data into a single entity. This keeps the data safe from outside interface and misuse. Objects allow procedures to be encapsulated with their data to reduce potential interference. One way to think about encapsulation is as a protective wrapper that prevents code and data from being arbitrarily accessed by other code defined outside the wrapper.

What do you understand by a variable?

Variable is a named memory location that can be easily referred in the program. The variable is used to hold the data and it can be changed during the course of the execution of the program.

What do you understand by numeric promotion?

The Numeric promotion is the conversion of a smaller numeric type to a larger numeric type, so that integral and floating-point operations may take place. In the numerical promotion process the byte, char, and short values are converted to int values. The int values are also converted to long values, if necessary. The long and float values are converted to double values, as required.

What do you understand by casting in java language? What are the types of casting?

The process of converting one data type to another is called Casting. There are two types of casting in Java; these are implicit casting and explicit casting.

What is the first argument of the String array in main method?

The String array is empty. It does not have any element. This is unlike C/C++ where the first element by default is the program name. If we do not provide any arguments on the command line, then the String array of main method will be empty but not null.

How can one prove that the array is not null but empty?

Print array.length. It will print 0. That means it is empty. But if it would have been null then it would have thrown a NullPointerException on attempting to print array.length.

Can an application have multiple classes having main method?

Yes. While starting the application we mention the class name to be run. The JVM will look for the main method only in the class whose name you have mentioned. Hence there is not conflict amongst the multiple classes having main method.

When is static variable loaded? Is it at compile time or runtime? When exactly a static block is loaded in Java?

Static variable are loaded when classloader brings the class to the JVM. It is not necessary that an object has to be created. Static variables will be allocated memory space when they have been loaded. The code in a static block is loaded/executed only once i.e. when the class is first initialized. A class can have any number of static blocks. Static block is not member of a class, they do not have a return statement and they cannot be called directly. Cannot contain this or super. They are primarily used to initialize static fields.

Can I have multiple main methods in the same class?

We can have multiple overloaded main methods but there can be only one main method with the following signature :

public static void main(String[] args) {}

No the program fails to compile. The compiler says that the main method is already defined in the class.

Explain working of Java Virtual Machine (JVM)?

JVM is an abstract computing machine like any other real computing machine which first converts .java file into .class file by using Compiler (.class is nothing but byte code file.) and Interpreter reads byte codes.

How can I swap two variables without using a third variable?

Add two variables and assign the value into First variable. Subtract the Second value with the result Value. and assign to Second variable. Subtract the Result of First Variable With Result of Second Variable and Assign to First Variable. Example:

int a=5,b=10;a=a+b; b=a-b; a=a-b;

An other approach to the same question

You use an XOR swap.

for example:

int a = 5; int b = 10;
a = a ^ b;
b = a ^ b;
a = a ^ b;

What is data encapsulation?

Encapsulation may be used by creating 'get' and 'set' methods in a class (JAVABEAN) which are used to access the fields of the object. Typically the fields are made private while the get and set methods are public. Encapsulation can be used to validate the data that is to be stored, to do calculations on data that is stored in a field or fields, or for use in introspection (often the case when using javabeans in Struts, for instance). Wrapping of data and function into a single unit is called as data encapsulation. Encapsulation is nothing but wrapping up the data and associated methods into a single unit in such a way that data can be accessed with the help of associated methods. Encapsulation provides data security. It is nothing but data hiding.

What is reflection API? How are they implemented?

Reflection is the process of introspecting the features and state of a class at runtime and dynamically manipulate at run time. This is supported using Reflection API with built-in classes like Class, Method, Fields, Constructors etc. Example: Using Java Reflection API we can get the class name, by using the getName method.

Does JVM maintain a cache by itself? Does the JVM allocate objects in heap? Is this the OS heap or the heap maintained by the JVM? Why

Yes, the JVM maintains a cache by itself. It creates the Objects on the HEAP, but references to those objects are on the STACK.

What is phantom memory?

Phantom memory is false memory. Memory that does not exist in reality.

Can a method be static and synchronized?

A static method can be synchronized. If you do so, the JVM will obtain a lock on the java.lang.
Class instance associated with the object. It is similar to saying:

synchronized(XYZ.class) {

}

What is difference between String and StringTokenizer?

A StringTokenizer is utility class used to break up string.

Example:

StringTokenizer st = new StringTokenizer("Hello World");

while (st.hasMoreTokens()) {

System.out.println(st.nextToken());

}

Output:

Hello

World