Contract-based discovery of Web services modulo simple orchestrators

Web services are distributed processes exposing a public description of their behavior, or contract. The availability of repositories of Web service descriptions enables interesting forms of dynamic Web service discovery, such as searching for Web services having a specified 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 successful client/service interaction.We study an equivalence relation that achieves both goals under the assumption that client/service interactions may be mediated by simple orchestrators. In the framework we develop, orchestrators play the role of proofs (in the Curry–Howard sense) justifying an equivalence relation between contracts. This makes it possible to automatically synthesize orchestrators out of Web services contracts.