Service-Oriented Computing - ICSOC 2007 Workshops
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Service-oriented computing is gaining wider acceptance. For Web services to become practical, an infrastructure needs to be supported that allows users and applications to discover, deploy, compose and synthesize services automatically. For this automation to be effective, formal semantic descriptions of Web services should be available. We propose a language called USDL (Universal Service-Semantics Description Language) for formally describing the semantics of Web services. USDL is based on the Web Ontology Language (OWL) and employs WordNet as a common basis for understanding the meaning of services. USDL can be regarded as formal service documentation that allows sophisticated conceptual modeling and searching of available Web services, automated service composition, and other forms of automated service integration. The design of USDL along with its formal specification in OWL is presented with examples. A theory of service substitution using USDL is presented. We formally define the Web service discovery and composition problem and present an approach for automatic service discovery and composition based on semantic description of Web services. We also report on an implementation of a semantics-based automated service discovery and composition engine that we have developed. This engine employs a multi-step narrowing algorithm and is efficiently implemented using constraint logic programming technology. The salient features of our engine are its scalability, i.e., its ability to handle very large service repositories, and its extremely efficient processing times for discovery and composition queries. We evaluate our composition engine on a Bioinformatics application for the automatic workflow generation of a phylogenetic inference task. We also evaluate our engine for automated discovery and composition on repositories of different sizes and present the results.