Multiview: A Methodology for Supporting Multiple Views in Object-Oriented Databases

A view in object-oriented databases (OODB) corresponds to virtual schema graph with possibly restructured generalization and decomposition hierarchies. We propose a methodology, called MultiView, for supporting multiple such view schemata. MultiView represents a simple yet powerful approach achieved by breaking view speciication into independent tasks: class derivation, global schema integration, view class selection, and view schema generation. Novel features of MultiView include an object algebra for class cus-tomization; an algorithm for the integration of virtual classes into the global schema; a view deenition language for view class selection, and the automatic generation of a view class hierarchy. In addition, we present algorithms that verify the closure property of a view and, if found to be incomplete, transform it into a closed, yet minimal, view. Lastly, we introduce the fundamental concept of view independence and show MultiView to be view independent.