View update in entity-relationship approach

摘要

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