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These three components of our new DCE can be as simple or as far- reaching as required. For example, both UDDI and ebXML provide similar services, one for the more simple cases, the other the more complex. Before we get into more specifics on each of these services, let's look at the standard Web Services model.

These three properties, when used in combination, provide a new form of Distributed Computing environment. The difference between this computing environment and DCEs of the past is in standards and implementations. A standard definition mechanism, standard lookup services, and standard transport definitions via Simple Object Access Protocol (SOAP). All of which are provided without concern for the underlying implementation mechanism. What makes Web Services so cool is that, at least in theory, a Web Service written in C and running on a Microsoft IIS can access a Web Service written in Java and running on BEA WebLogic Server. All without concern for how each Web Service is actually implemented.

A way to define what the input and output parameters are for such a

A transport mechanism to access a service.

A way to find and register interest in a service.

But what exactly is a Web Service in the first place? Well, I'm sure BEA, Microsoft, Ariba, HP, Sun and others all have their own particular definitions; however, for the sake of argument, a Web Service is three specific things:

Over the past six to twelve months we've begun to see a new Web programming paradigm, that of the Web Service. But exactly what are these Web services anyway? In a nutshell, Web Services are the natural evolution of basic Remote Procedure Calls. In fact, we shall see that Web Services are in fact not a much more advanced technology than RPC of the past, but similar concepts applied in new ways!

What are Web Services, Anyway?

In this article we shall examine traditional approaches to electronic collaboration, see the various system services required to solve collaboration problems, and examine how Web Services and J2EE provide these services. In future articles we shall look at each service in detail and develop our own Web Services on top of existing Web applications, exporting these services to the Web community at large.

Web Services have at their core XML as a mechanism for communication. Ultimately, Web Services are based on three specific technologies: a mechanism to register a service, a mechanism to find a service, and a mechanism for two parties to communicate. Today, developers can use the Java 2 Enterprise Edition APIs and XML to provide Web Services. Such developments leverage existing Web sites and provide simple methods to extend, interconnect and publish existing J2EE-based applications in new and exciting ways.

Web Services are a new technology that could revolutionize the way business-to-business and business-to-consumer services are provided. Web Services use a variety of technologies to allow two applications to communicate. However, none of these are new claims; what makes Web Services different from other similar mechanisms are the technologies which provide the service.

Java and Web Services Primer - O'Reilly Media