Contract-directed Synthesis of Simple Orchestrators

The availability of repositories of Web service descriptions enables interesting forms of dynamic Web service discovery, such as searching for Web services exposing a specified behavior – or contract. This calls for a formal notion of contract equivalence satisfying two contrasting goals: being as coarse as possible so as to favor Web services reuse, and guaranteeing smooth client/service interaction. We study an equivalence relation under the assumption that interactions are controlled by orchestrators. We build a simple orchestration language on top of this theory and we show how to synthesize orchestrators out of Web services contracts.