Abstract. Service composition is gaining momentum as the potential silver bullet for the envisioned Semantic Web. It purports to take the Web to unexplored efficiencies and provide a flexible approach for promoting all types of activities in tomorrow's Web. Applications expected to heavily take advantage of Web service composition include B2B E-commerce and E-government. To date, enabling composite services has largely been an ad hoc, time-consuming, and error-prone process involving repetitive low-level programming. In this paper, we propose an ontology-based framework for the automatic composition of Web services. We present a technique to generate composite services from high-level declarative descriptions. We define formal safeguards for meaningful composition through the use of composability rules. These rules compare the syntactic and semantic features of Web services to determine whether two services are composable. We provide an implementation using an E-government application offering customized services to indigent citizens. Finally, we present an exhaustive performance experiment to assess the scalability of our approach.

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Mapping out the challenges and strategies for the widespread adoption of service computing.

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Abstract-Data-Providing (DP) services allow query-like access to organizations' data via web services. The invocation of a DP service results in the execution of a query over data sources. In most cases, users' queries require the composition of several services. In this paper, we propose a novel approach for querying and automatically composing DP services. The proposed approach largely draws from the experiences and lessons learned in the areas of service composition, ontology, and answering queries over views. First, we introduce a model for the description of DP services and specification of service-oriented queries. We model DP services as RDF views over a mediated (domain) ontology. Each RDF view contains concepts and relations from the mediated ontology to capture the semantic relationships between input and output parameters. Second, we propose query rewriting algorithms for processing queries over DP services. The query mediator automatically transforms a user's query (during the query rewriting stage) into a composition of DP services. Finally, we describe an implementation and provide a performance evaluation of the proposed approach.