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

There has been an explosion in the types, availability and volume of data a ccessible in an information system, thanks to the World Wide Web (the Web) and related inter-networking technologies. In this environment, there is a critical need to replace or complement earlier database integration approac hes and current browsing and keyword-based techniques with concept-based ap proaches. Ontologies are increasingly becoming accepted as an important par t of any concept or semantics based solution, and there is increasing reali zation that any viable solution will need to support multiple ontologies th at may be independently developed and managed. In particular, we consider t he use of concepts from pre-existing real world domain ontologies for descr ibing the content of the underlying data repositories. The most challenging issue in this approach is that of vocabulary sharing, which involves deali ng with the use of different terms or concepts to describe similar informat ion. In this paper, we describe the architecture, design and implementation of the OBSERVER system. Brokering across the domain ontologies is enabled by representing and utilizing interontology relationships such as (but not limited to) synonyms, hyponyms and hypernyms across terms in different onto logies. User queries are rewritten by using these relationships to obtain t ranslations across ontologies. Well established metrics like precision and recall based on the extensions underlying the concepts are used to estimate the loss of information, if any.