A Metadata Based Approach to Improving Query Responsiveness

We describe a rule-based approach to semantic speci cation that can be used to dynamically establish semantic relevance between consumers' queries posed on the y and producers' data sources available online. The semantic speci cation of user queries is independent of the content and capabilities of the data sources (query-to-source independence). The semantic speci cation of the content and capability of a data source is independent of the content and capability descriptions of other sources (sourceto-source independence). Query processing techniques use these speci cations along with the query modi cation and transformation routines to perform relevance reasoning and to guarantee semantically correct query answers. This work also examines the e ect of changing metadata semantics, such as changes in the content and capabilitiy descriptions of data sources or the user query pro le speci cations. Methods are described for detecting these changes and for determining if the information sources can continue to supply meaningful data to answering consumers' queries. These methods and transformation routines are necessary for determining logical connectivity between information producers and information consumers and for establishing dynamic interconnection between a growing collection of data sources and a consumer's query.