A deductive rule-based language for object-oriented databases is presented. A deductive rule in this language derives new patterns of associations among objects of some selected classes if these objects fall in certain 'base' on other derived patterns. The patterns of object associations derived by a rule are held in a subdatabase whose intention consists of some selected classes and their associations. In other words, the structure of a derived subdatabase is represented using the structural constructs provided by the object-oriented data model and hence can be uniformly operated on by other rules to further derive new subdatabases. Therefore, the world of subdatabases is closed under this rule-based language.
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