Advanced Mechanisms for Service Composition, Query and Discovery

One of the ultimate goals of Service Oriented Computing (SOC) is to provide support for the automatic on-demand discovery of basic functionalities that, once combined, correctly compute a user defined task. To this aim, it is necessary for services to come equipped with a computer-understandable interface that allow applications to match the provided functionalities with the user needs. In this context, a prominent issue concerns the compliance between the operations invoked by the client – the client protocol – and the operations executed by the service – the service protocol. Process calculi, the theoretical tools investigated in the Work Package 2 of Sensoria, can contribute to the solution of this problem. The idea we present in this chapter is to describe the externally observable message-passing behaviour of services as process calculi expressions; following recently adopted terminology, we call this description the service contract. We show how, in certain cases, service contracts can be automatically extracted out of service behaviour, and how they can be used to formally check the compliance among the communication protocols of interacting services.