Here is another way to understand how Web services work. Web services directories and protocols essentially serve three functions: publish, find, and bind. To use Web services, applications are:
Published in a common UDDI directory (such that cooperating applications can find each other);
Found (using WSDL protocols that can locate Web services applications and determine if those applications can work with the source application); and
Bound (a communications link between the two applications is established, so that a service such as performing some sort of calculation or transaction can be rendered using SOAP protocols).
These three service elements and their relationship to requester, broker, and provider services are illustrated in Figure 1-1.
In this illustration a service requester is either you or your source application. The requester initiates the request for a Web service application. The Service Provider is the Web services application itself. The Service Broker can be a company that provides lists and information about Web services programs, or a Service Broker can refer to the programmatic process that helps locate an application and helps the two cooperating applications determine how to best communicate.