Advanced Messaging:Reliability and Sessions

Advanced Messaging:Reliability and Sessions

Customers of web services often request several advanced messaging features. The most requested feature, of course, is message-based security (refer to Chapter 13); however, reliable messaging, sessions, and eventing protocols are also needed.

Reliability includes a continuum of features. The Web service architecture offers several specifications that together can form a reliable messaging architecture. These range from WS-Routing for specifying routes that SOAP messages should take, to specifications for reliability (not yet released as of this writing). This chapter covers features that deliver sessions, reliability, and even eventing, and which you can use individually or in combination. Because SOAP is so modular, you can create a lightweight application by using only the pieces you need.

Because there are no specifications or even drafts of specifications available at this time, this chapter focuses on the ideas behind potential specifications. Over time, these concepts will continue to be applicable, but the syntax introduced here is only for this book, and does not reflect any company's specific ideas.

Note too that this chapter is in no way a complete discussion of what it takes to build a reliable messaging system. Rather, it presents the basic ideas. The specific implementation details are left to the reader, as they vary according to the type of application being built. In the near future, look for the release of generic reliable messaging systems that provide most of this functionality.