VIEW UPDATE IN ENTITY-RELATIONSHIP APPROACH

The traditional problem of updating relational databases through views is an important practical problem that has attracted much interest. I n this paper, we examine the problem of view update in Entity-Relation ship based database management systems [1] where the conceptual schema is represented by a normal form ER diagram [2] and views may be model led by ER diagrams. We develop a theory within the framework of the ER approach that characterizes the conditions under which there exist ma ppings from view updates into updates on the conceptual schema. Concep ts such as virtual updates and three types of insertability are introd uced. We also present two algorithms, the View Updatability Algorithm and the View Update Translation Algorithm.