Asynchronous messaging between Web services using SSDL

The SOAP Service Description Language (SSDL) is designed for describing asynchronous, message-oriented, and multimessage interactions between Web services. SSDL provides the basis for a range of protocol description frameworks. At one end of the spectrum, such frameworks can be simple, SOAP-centric replacements for the Web Services Description Language. At the other end, they're a more expressive contract-definition language enabling formal verification of asynchronous application protocol properties. This is possible because SSDL focuses on the "message" abstraction as the building block for service-oriented applications.