Multiple views and abstractions with an extended-entity-relationship model

The features of the Entity-Relationship model are examined, as a means for representing both the conceptual schema and the external schema in a database system. In order to serve in this dual capacity, its modelling features are extended to support multiple user views. We show how to represent a model and present a suitable diagrammatic technique. To represent these concepts at the user level we propose a data definition language with a concise and simple structure. Furthermore, guidelines are given for interfacing the E-E-R schema with existing DBTG-like systems.