Separating Per-client and Pan-client Views in Service Specification

Service-oriented architecture is predicated on the availability of accurate and universally-understandable specifications of services which capture all the information that a potential user needs to know to use the service. However, WSDL, the most widely used service specification standard, only allows the syntactic signatures of the operations offered by a service to be described. This not
only makes it difficult to specify context sensitive information, such as acceptable operation invocation sequences and drive service discovery through client- oriented requirements, it is also an inappropriate level of abstraction for a human friendly description of a service’s capabilities. The current thinking is that context sensitive information such as operation sequencing rules should be described in an accompanying specification document written in an auxiliary language. For example, WS-CDL is a well known auxiliary language for writing choreography descriptions that capture interaction scenarios in terms of abstract roles and participants. However, this approach not only decouples the additional information from the core WSDL specification, it also describes it in terms of abstractions which may not match those used (implicitly or explicitly) by the service. In this paper we investigate this issue in greater depth, explore the different solution patterns and propose a new specification approach which rectifies the identified problems.