Dealing with Relationship Cardinality Constraints in Relational Database Design

Abstract

Conceptual models are well-known tools to achieve a good design of information systems. Nevertheless, the understanding and use of all the constructs and constraints which are presented in such models are not an easy task and sometimes it is cause of loss of interest. In this chapter we have tried to study in depth and clarify the meaning of the features of conceptual models. The disagreements between main conceptual models, the confusion in the use of some of their constructs and some open problems in these models are shown. Another important topic treated in this chapter is the conceptual-to-logic schemata transformation process. Some solutions are presented in order to clarify the relationship construct and to extend the cardinality constraint concept in ternary relationships. How to preserve the cardinality constraint semantics in binary and ternary relationships for their implementation in a DBMS with active capabilities has also been developed.