The Role of Service Discovery
In previous chapters, we have examined SOAP and service description mechanisms. But, how does the requestor know where to send the SOAP message? What kind of message should the requestor send to properly invoke the Web service? These questions can be addressed by the Web service's description. In a service-oriented architecture, Web services metadata (especially its service description) is key to maintaining loose coupling between service requestors and service providers.
In Chapter 6, "Describing Web Services," we discussed Web Services Description Language (WSDL), the most popular mechanism of service description for Web services. But in order for a Web service to be invoked, it must be discovered somehow. How was the business partner discovered, establishing the potential relationship between service requestor and service provider? How did the service requestor find out about the services provided by a service provider? How did the requestor obtain the WSDL service description from the service provider? Addressing these questions is the role of the service registry within a service-oriented architecture.