Dynamic Discovery, Invocation and Composition of Semantic Web Services

摘要

In this paper we described the importance of the Semantic Web in the development of the Web services infrastructure and the contribution provided by OWL-S; furthermore, we showed that OWL-S is not just an academic exercise, but it can be used to control the interaction between Web services that use the Semantic Web, thus leading the way towards Semantic Web services. Specifically, we used OWL-S to describe capabilities of Web services so that they can find each other on the basis of the information that they provide, rather than incidental properties such as their name, port, or a free text description. Furthermore, we showed how OWL-S can also be used to control the autonomous interaction between Web services without any need of preprogramming hard coding neither the sequence of messages to exchange nor the information to be transmitted. The work presented here shows the importance of the Semantic Web and the need for widespread ontologies. In the Web service discovery phase, ontologies support the basic information on the changes that result by the execution of Web services; the representation of those changes needs to refer to objects or concepts in the world for which all the parties in the transaction need to have a shared knowledge and understanding. Furthermore, ontologies provide an inference framework that allows Web services to resolve discrepancies and mismatches between the knowledge that they are using. This is particularly relevant in the OWL-S/UDDI matching engine that has to abstract from the superficial differences between the advertisement and the request to recognize whether they describe the same capabilities. In addition, ontologies play an essential role during Web services interaction, because they provide a shared dictionary of concepts so that Web services can understand each other's messages. Ultimately, ontologies provide the basis for the use of the knowledge exchanged by Web services by supporting inferences when new knowledge is added.