Introduction to the special issue on the use of entity-relationship concepts in databases and related software

Abstract

This is a collection of selected papers from the Third International Conference on Entity-Relationship (ER) Approach. These papers deal with the development of both principles and pragmatics of the ER approach in computer data engineering and reflect the trends of the expanding and maturing nature of the ER concept in the areas of database logical design, data management and control, database-oriented tools development, and reliability control in distributed database systems. The first five papers address the theory of entity relationships and foundations of the field of the ER approach. In conceptual schema design of databases, both structural and behavioral analyses of data based on the ER approach are discussed separately by Kent, Jajodia and Ng, and Sakai. The paper by Kent describes a methodology for data analysis leading to logical database design, based upon identifying the facts about entities that are to be maintained in a database, in terms of relationships among entities that are aggregated into data records: one record per fact rather than one record per entity. In contrast, most methodologies focus on entities and suggest that data represents two kinds of facts: facts about things (attributes) and facts that connect things (relationships). This implies that the distinction between relationships and attributes has to be made in the design process and design schemes have to proceed in two stages, one for handling relationships and the other for handling attributes. Above all, most methodologies assume that a simple representation is available for all entities. However, in reality, represen-