Reliability is measured by a system’s ability to deliver messages from point A to point B without error. Figure 2–5 shows the specifications that were implemented to ensure reliable delivery of messages between two web services endpoints.
In addition to the Core XML specifications and supporting standards (Web Services Security and Web Services Policy, which are required building blocks), the reliability feature is implemented using the following specifications:
Web Services Reliable Messaging: This specification defines a standardized way to identify, track, and manage the reliable delivery of messages between exactly two parties, a source and a destination, so as to recover from failures caused by messages being lost or received out of order. The specification is also extensible so it allows additional functionality, such as security, to be tightly integrated. The implementation of this specification integrates with and complements the Web Services Security, and the Web Services Policy implementations.
Web Services Coordination: This specification defines a framework for providing protocols that coordinate the actions of distributed applications. This framework is used by Web Services Atomic Transactions. The implementation of this specification enables the following capabilities:
Enables an application service to create the context needed to propagate an activity to other services and to register for coordination protocols.
Enables existing transaction processing, workflow, and other coordination systems to hide their proprietary protocols and to operate in a heterogeneous environment.
Defines the structure of context and the requirements so that context can be propagated between cooperating services.
Web Services Atomic Transactions: This specification defines a standardized way to support two-phase commit semantics such that either all operations invoked within an atomic transaction succeed or are all rolled back. Implementations of this specification require the implementation of the Web Services Coordination specification.