View creation for queries in object oriented databases
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A view in object oriented databases corresponds to virtual schema with restructured generalization and decomposition hierarchies. Numbers of view creation methodologies have been proposed. A major drawback of existing methodologies is that they do not maintain the closure property. That is, the result of a query does not have the same semantics as embodied in the object oriented data model. Therefore, this paper presents a view creation methodology that derives a class in response to a user's query, integrates derived class in global schema (i.e., considers the problem of classes moving in class hierarchy) and selects the required classes from global schema to create the view for user's query. Novel idea of view creation includes: (a) an object algebra for class derivation and customization (where the derived classes in terms of object instances and procedure/methods are studied), (b) maintenance of closure property, and (c) classification algorithm which provides mechanism to deal with the problem of a class moving in a class hierarchy.
Keywordsobject manipulation type level operation instance level operation object algebra object operator operator syntax operator semantics derived class class integration view creation algorithm
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