Automatic composition of transition-based semantic web services with messaging

In this paper we present Colombo, a framework in which web services are characterized in terms of ( i ) the atomic processes (i.e., operations) they can perform; ( ii ) their impact on the "real world" (modeled as a relational database); ( iii ) their transition-based behavior; and ( iv ) the messages they can send and receive (from/to other web services and "human" clients). As such, Colombo combines key elements from the standards and research literature on (semantic) web services. Using Colombo, we study the problem of automatic service composition (synthesis) and devise a sound, complete and terminating algorithm for building a composite service. Specifically, the paper develops ( i ) a technique for handling the data, which ranges over an infinite domain, in a finite, symbolic way, and ( ii ) a technique to automatically synthesize composite web services, based on Propositional Dynamic Logic.