Integrated database system and program storage medium

摘要

By corresponding the external databases to the predicates used in query processing according to a predetermined ontology, it is allowed to issue a query through the ontology. The query thrown into the integrated database is expanded into the set of approximate queries according to approximation rules provided in the ontology. The optimization module refers to the query capability of the external databases to perform the query optimizing in which these approximate queries can be executed efficiently as a whole.