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Web Services are one of the most talked about and hyped features of the Internet. In fact some people are saying that Web Services are one of the few, revolutionary ideas currently within the IT industry and that Web Services have the potential to change the world as we know it.
Web Services expose server-side objects and methods that expose application functionality across the Web. Web Services themselves are actually written on the server-side in a language such as ColdFusion, Microsoft .NET, or J2EE. For example, we could write a web service that would check our inventory from a database by accessing this information across the Web as well as from other applications.
There are public Web Services available that do everything from translating text to checking the latest traffic conditions in southern California. The most revolutionary part of Web Services is that other applications can call web service methods to extend their own functionality and not be concerned about the language in which the web service was written or on what platform it runs.
Web Services send information by means of extensible markup language (XML) packets, which means they can handle complex data structures. The beauty of XML is that it is completely platform independent. Server-side solutions, client-side solutions, and even desktop suites (such as Microsoft Office) can consume XML. When we consume Web Services in Flash, we do not need to know in what language the web service was written; we only need to know the data structures that the method returns by means of XML.
Before the advent of Web Services, the only way to expose methods to applications was through the use of a proprietary protocol, such as Remote Procedure Call (RPC), Remote Method Invocation (RMI), or Common Object Request Broker Architecture (CORBA). Developers had to choose a protocol and manually expose each method. Web Services are revolutionary because they make it easy to connect applications to other applications in a platform-independent way.
The key to Web Services is that they provide a uniform way for applications to communicate with one another using the Web Services Description Language (WSDL), which is just a special type of XML. Communication is achieved through the Simple Object Access Protocol (SOAP), which virtually all platforms can consume and generate. The WSDL description language, SOAP, and the Universal Description, Discovery and Integration (UDDI) standards provide a uniform, standard method of communication, which means Flash can easily work with any server-side solution. You'll learn about all this and more in the coming sections of this chapter.
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