In recent years the development of ontologies—explicit formal specifications of the terms in the domain and relations among them (Gruber 1993)—has been moving from the realm of Artificial-Intelligence laboratories to the desktops of domain experts. Ontologies have become common on the World-Wide Web. The ontologies on the Web range from large taxonomies categorizing Web sites (such as on Yahoo!) to categorizations of products for sale and their features (such as on Amazon.com). The WWW Consortium (W3C) is developing the Resource Description Framework (Brickley and Guha 1999), a language for encoding knowledge on Web pages to make it understandable to electronic agents searching for information. The Defense Advanced Research Projects Agency (DARPA), in conjunction with the W3C, is developing DARPA Agent Markup Language (DAML) by extending RDF with more expressive constructs aimed at facilitating agent interaction on the Web (Hendler and McGuinness 2000). Many disciplines now develop standardized ontologies that domain experts can use to share and annotate information in their fields. Medicine, for example, has produced large, standardized, structured vocabularies such as SNOMED (Price and Spackman 2000) and the semantic network of the Unified Medical Language System (Humphreys and Lindberg 1993). Broad general-purpose ontologies are

Abstract—The success of web service is to interact with the applications of different domains. To achieve this interoperability, dynamic discovery of web services is essential. The repository of the web service needs an index of the currently available web services on the internet, which can be done by explicit publishing by the developers or by addition of the web services using crawlers. There is a chance that web services are indexed, but in real not available permanently or temporarily due to some reasons. We propose the use of OSIAN (Ontology based Service Index Annotator) to check the web services as availability which can be currently used by the service consumers. This will be of great use for the service consumers as the time taken to search for the web services among a large set of provisioned web services listed out in the repository will be reduced. Index Terms—availability, ontology, repository, web services I.

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