Observer: an approach for query processing in global information systems based on interoperation across pre-existing ontologies

The huge number of autonomous and heterogeneous data repositories accessible on the "global information infrastructure" makes it impossible for users to be aware of the locations structure/organization, query languages and semantics of the data in various repositories. There is a critical need to complement current browsing, navigational and information retrieval techniques with a strategy that focuses on information content and semantics. In any strategy that focuses on information content, the most critical problem is that of different vocabularies used to describe similar information across domains. We discuss a scalable approach for vocabulary sharing. The objects in the repositories are represented as intensional descriptions by preexisting ontologies expressed in Description Logics characterizing information in different domains. User queries are rewritten by using interontology relationships to obtain semantics preserving translations across the ontologies.