The multi-layered schema of an extended entity-relationship model /

Abstract

In a database design process, the database model used is essential for producing a good conceptual schema. In some database models, like IMS and CODASYL, a conceptual schema contains too many implementation details which complicate the designer's task. The conceptual schema of a relational database hides too much information from the user, because it lacks the necessary structure. The standard E-R model has more structure and is easy to use. But, it still lacks the ability to express certain types of abstract concepts needed in most design processes. In this work, the E-R Model is extended to include generalization abstraction among different sets of a database. The generalization structures and their components form the conceptual schema of a database. The schema is represented by a multi-leveled diagram. A user is provided with a set of diagram operators to view parts of a diagram relevant to him. A top down design technique based on data dependencies and inapplicability of attributes is also presented for this database model.