Design and implementation of derived entities

Abstract

To allow an utilization of database system trigger mechanisms and application generators for information systems implementation, entity derivation is introduced into the ER model as a semantic equivalent for derived tuples and derived attributes. The necessity of an open, reusable representation of data derivation in information systems engineering is discussed. A tool is presented that supports not only the semantic design of entity types, existential dependencies, and aggregation/generalization relationships, but also the design of derivation relationships. Based on three basic types of parametrical trigger declarations, the system specification created by the design tool can then be transformed automatically into database triggers by an object generator. Object generator design is presented, and the trigger parameter substitution process is described. Based on the design and implementation of a MRP II-style, complex production management system for a large mechanical engineering company, the benefits of the proposed extension of traditional, ER-based approaches to information systems design and implementation are discussed.