Searching for Semantic Web Services - A Google based approach

Semantic Web Service discovery and selection are a very time and resources consuming task. They require reasoning support for the matchmaking of the capabilities of services against user defined goals and constituent sub- goals, and for the mediation of the domain knowledge used to describe the different relevant aspects of services. This paper presents a performance study around the number of times the reasoner has to be used in nowadays initiatives. Such study lays the basis for an innovative approach inspired in the popular search engine Google, which tries to improve the performance of the whole process. The main idea is to carry the reasoning as an off-line task, storing the output for later reuse. It also elaborates on the idea of making service descriptions and goals available independently of registries or repositories, i.e. Web pages. Such idea permits to profit, extend and further reuse, well established concepts developed by popular search engines, thus assimilating service discovery and selection to any other type of search engine task. capabilities of the different available services against the description of the goal that the end user aims to achieve. Finally, during selection and based on the non-functional properties of the service, the most appropriate ones, e.g. the most reliable and cost effective ones, among the discovered services are selected. A common feature to discovery and selection is that a reasoner engine is required in order to match goals and capabilities (discovery), and to mediate among domain specific terminologies (selection and discovery). Essentially the user goal is decomposed into constituent sub-goals which need to be individually matched against the capabilities of registered services, requiring the alignment of the terminology used to describe capabilities and sub-goals. During the selection phase mediation is also required in order to align the different vocabularies used to describe non-functional properties. It could be included as part of the goal-capability mediation in order to save resources. In general, the number of times that the reasoner needs to be used for goal-capability matching and mediation is really big, growing as the number of available services and vocabularies grows. In this paper an approach based on the popular search engine Google is presented, which tries to solve some of the performance limitations presented by discovery. It revolves around the idea of making the process in an off-line fashion, keeping a list of goals and sub-goals that include references to the services whose capabilities can satisfy them, minimizing the impact of the reasoning in the discovery and selection tasks. It also proposes to publish the description of services and goals independently of the registries and repositories respectively, making it available like any other Web resources, i.e. Web page. This approach allows the reuse of the concepts and ideas already developed for search engines, permitting to extend them and further reusing them in regard to Web Services, thus understanding the goal-capability matching like any other type of search. A performance study in regard the number of times the reasoner has to be used in the case that previously carried reasoning tasks are not stored is presented, setting the basis that allow elaborating and justifying the necessity of a new proposal.