VIEW UPDATES FOR AN EXTENDED ENTITY-RELATIONSHIP MODEL

Recently, several graphical query languages have emerged that allow users to manipulate a database schema with diagram-manipulation operators until the modified schema represents the view of the data that satisfies a user query. The research in this area has also shown how updates can be graphically specified and how updates propagate for various semantic models. In this paper we continue this work by investigating view definition and view updates for an extended entity-relationship model. We define views by invoking diagram-manipulation operators to transform an original schema into a view schema. Our diagram-manipulation operators have an object-traceability property that allows us to trace the identity of any entity object in any view to a unique entity object in the underlying database and to trace the identity of any relationship object in any view either to a unique relationship object or to a unique set of component relationship objects in the underlying database. Based on object traceability, we define and discuss properties of update operators to modify, insert, and delete objects in views,