This part begins the journey into the domain of quality-of-service characteristics of Web service interactions with a discussion of reliable interactions. The figure that follows shows where this topic falls in the Web services stack.
Chapter 10, "Reliable Messaging," discusses the WS-Reliable Messaging (WS-RM) specification. WS-RM defines protocols for establishing and maintaining a reliable interaction between a client and a service. It supports several different qualities of service, such as in-order and exactly-once delivery.
The second chapter in this section, Chapter 11, "Transactions," discusses a venerable topic that is key to enabling business interactions using Web services: how Web services can agree on the outcome of multiparty interactions. This chapter presents two protocols: WS-Atomic Transactions for atomic transactions with ACID properties, and WS-Business Activity for loosely coupled coordination, where intermediate steps are visible to the participants. Both protocols are built on top of the WS-Coordination specification, which provides a framework for developing distributed coordination protocols.