The need of capability requirements inside choreographies and interaction protocols

A typical problem of research in the area of Service-Oriented Systems is the composition of a set of services for executing a complex task. In this paper we face an instance of this problem in which a set of parties (be they peers, agents or systems) have to interact according to a given choreography. In particular, we mean to exploit the role definitions contained in the choreography for realizing interaction policies that can be executed by the involved parties. In this case it is necessary that the choreography captures not only the interactive behavior of the system as a whole but that the role definitions contain also a set of requirements of capabilities that the parties should exhibit, where by the term “capability” we mean the skill of doing something or of making some condition become true. Such capabilities have the twofold aim of connecting the interactive behavior to be shown by the role-player to its internal state and of making the policy executable.