Towards Automatic Web Service Discovery and Composition in a Context with Semantics, Messages, and Internal Process Flow (A Position Paper)

In this short position paper we briefly describe our recent and on-going work on 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. In particular, Colombo complies with key aspects of the emerging Semantic Web Services Initiative (SWSI) Ontology, including representation of atomic processes (that impact an abstraction of the “real world”) and messages (for data flow between web services), along with a concrete model of the process and data flow within web services. Using Colombo, we are studying the problem of automatic service discovery and composition (synthesis). In [5, 4], we devise a sound, complete and terminating algorithm for building a composite service (or determining that none exists) under various restrictions. Specifically, this work 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. We view this as an important first step in the eventual development of practical techniques for automatic discovery and composition of web services that are described using the emerging SWSI ontology. Service Oriented Computing (SOC [1]) is the computing paradigm that utilizes web services (also called e-Services or, simply, services) as fundamental elements for realizing distributed applications/solutions. Web services are self-describing, platform-agnostic computational elements that support rapid, low-cost and easy composition of loosely coupled distributed applications. SOC poses many challenging research issues, the most prominent being web service composition. Web service composition addresses the situation when a client request cannot be satisfied by any available service, but by suitably combining “parts of” available services. Composition involves two different issues [1]. The first, typically called composition synthesis, is concerned with synthesizing a specification of how to coordinate the component services to fulfill the client request. Such a specification can be produced either automatically, i.e., using a tool that implements a composition algorithm, or manually by a human. The second issue, often referred to as orchestration, is concerned with how to actually achieve the coordination