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UDDI stands for Universal Discovery, Description, and Integration. UDDI is a repository of Web Services and companies that provides Web Services to the public and other companies. UDDI also contains business information for corporations that work in this arena. The repository concept evolved from the concept of Business to Business (B2B) exchanges working furiously to collaborate across the Web. Prior to the UDDI standard, there was not a way for these exchanges to easily find each other, much less the functionality they needed to share. By having a standard place in which a corporation may search for partners, the collaboration process moves forward at a quicker pace.
Several major vendors host the UDDI repositories, such as Microsoft and IBM, as a service to the Web Service community. There is currently no charge to use any part of the implementation. Each vendor that hosts a repository ends up replicating with the other partners so that they should contain the same information. Therefore, when you use the repository it shouldn’t matter which vendor’s implementation you consider.
You contact the repository in one of two ways: either through a Web browser or through SOAP requests and responses by using a particular API. This gives you great flexibility because you can either search yourself or create tools to automatically search the repository on a regular basis, looking for functionality you might need.
The UDDI standard confuses many because it encompasses many things, much like the SOAP standard. SOAP not only describes the contents of a Web Service but also describes how the messages are transmitted and much more. UDDI defines how a repository operates and how the Web Services and corporations are described with XML along with the API for contacting the repository with an application.
The repository of information contains three different sets of data. The first is general contact information, which includes street address and perhaps an individual responsible for fielding inquiries. Searching for the type of service, such as stock quotes, is also available along with information about the type of industry a particular company resides in. By thinking of UDDI as a combination of the white and yellow pages for Web Services and businesses, you begin to get a clearer picture of how to take advantage of UDDI.
Links to WSDL files are often found at a UDDI site, but they do not share any formal relationship. UDDI tells you where the Web Service resides and who sponsors it. On the other hand, WSDL describes the Web Service, including which methods are available. When trying to discover Web Services, you often find that a UDDI site leads you to a WSDL file—that’s why the misconception that they are related exists.
If you need to be compatible with Microsoft’s .NET environment, look in the repository for Web Services that have a URL for the WSDL file. .NET Web Services need this to create a proxy dll (or a Web reference in Visual Studio.NET) to use the methods in that Web Service. Chapter 6 introduces .NET Web Services and describes how to use the WSDL file appropriately.