Chapter 5. Web Services Addressing
SOAP introduces an extensible message format and a common processing model with the purpose of enabling different protocols and interaction patterns. Other specifications define, in a modular, composeable way, the additional artifacts and conventions required to support specific behaviors and protocols. First and foremost, mechanisms must be provided to ensure that messages are correctly delivered to the appropriate destination, or service endpoint. Web Services Addressing defines these mechanisms.To provide these mechanisms, it's necessary to resolve at least two different problems. The first is how to identify Web service endpoints. Before this chapter can begin to discuss how the Web services infrastructure will direct messages to their destinations, one must understand how to represent such "destinations" using a certain XML dialect. This problem is more subtle than it might appear at first sight, when it's approached from a Web-only perspective, as opposed to a Web services or service-oriented perspective. That's because of the rich and dynamic nature of Web service interactions as compared to traditional Web requests. The second problem is how to communicate these endpoint identifiers (or "endpoint references") in the course of a Web services exchange. For example, how to encode endpoint references in a SOAP message as SOAP headers, and what is the precise meaning and processing model for those endpoint references? Here, again, the rich nature of the service-oriented interaction model calls for careful design.The goal of the WS-Addressing specification is to provide the means to identify a Web service endpoint and a way to use such identifiers in SOAP messages for the delivery and exchange of messages between Web service providers and Web service requesters. Together, these two mechanisms define a simple yet powerful solution to the problem of how to address a Web service endpoint. |
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