The example above only shows part of what the WSDL file contains. If would also contain definitions on how to handle the response output, i.e. send our daily quote, author and website address. Because of space constraints I elected not to show you a complete WSDL file example but the portion above should give you an excellent idea of how large and involved a WSDL file can become.
UDDI, Have You Seen My Web Service?
Lastly, there is the optional Web Service piece known as the UDDI (Universal Description, Discovery and Integration). This is a platform-independent framework that is designed to provide a directory where Web Services can be discovered. Think of it as a bulletin board for posting Web Services. It uses SOAP for communication and WSDL to provide the information about each Web Service. While this is by no means a requirement for creating or using a Web Service, it does offer a convenient way to find and consume Web Services in your own applications.
As with all technology, Web Services are an evolving technology that may undergo some significant changes over the next several years. However, the root concept of a technology independent platform for the requesting and receiving of data from disparate applications over the internet will likely be with us for the foreseeable future. There are several companies now that already put a lot of time, money and effort into developing and advertising their Web Services. Amamzon.com Web Services is a prime example of this kind of effort. If you want to learn more about XML, SOAP or even WSDL, a great source for introductory tutorials can be found on the W3C website.