Highlights of XML Web services XML

In today's business scenario, people need scalable and reliable multi-user applications. This need has led to a shift from traditional desktop applications to distributed applications.

A traditional desktop application is a monolithic entity. All the functionality is built into a single application. Therefore, when you make a change in the application, you need to recompile and redistribute the entire application. This results in an increase in the overall cost of deploying the application. In addition, desktop applications have a limited access to another's processes and data. Therefore, upgrading these applications have a limited access to another's processes and data. Therefore, upgrading these applications so that they can cope with the increasing requirements is difficult. Consequently, distributed applications were developed.

A distributed application is a scalable application. The functionality of the distributed applications is spread across various modules or tiers as listed:

  • Presentation tier
  • Business logic, or middle, tier
  • Data tier

For example, consider a distributed application that consists of a database forming the data tier. You can access the data in the database from a client application, which forms the presentation tier. You access the data by using an intermediate application. This intermediate application provides the business logic and forms the middle tier. Traditionally, in distributed applications, the middle tier is developed using technologies, such as COM and CORBA.

With distributed applications, you do not need to maintain the database, the client application, and the intermediate application on the same computer. In most cases, the client application and the database are present on separate remote computers.

Distributed applications, which are highly efficient, are created using architectures, such as DCOM, CORBA, RMI, and so on. The distributed applications that use these architectures depend on protocols that are specific to respective technologies and architectures, which 37 reduces the usability of these models for developing cross-platform applications. As a result, Web services are being considered as an alternative that allows you to create distributed applications that are interoperable. This implies that Web services make data available to applications that run on multiple platforms and are developed using multiple technologies.

For example, when you create a Web service, you can access it from applications created using various languages such as Visual Basic, Java, Delphi, and so on. In addition, you can access the Web service from applications that run on various operating systems, such as Windows, Linux, or Solaris.

This chapter gives you an overview of Web services. It also discusses the architecture of Web services, the components, and the technologies involved in the creation of a Web service. In subsequent chapters, you will learn how to create these services by using various programming languages.

You can create Web services by using several programming languages, such as Visual C#, Visual Basic .NET, and Java. Because Web services use XML for transferring data, Web services are also referred to as XML Web services.

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