FUNDAMENTALS OF CARDINALITY CONSTRAINTS

The Entity-Relationship model is frequently used during conceptual database design phases. However, this model can be enriched and then used for the complete lifecycle of a database as an interface model. For this purpose, the concepts of the ER-model need to be theoretically well-founded. The aim of this paper is to show how the theoretical basis of one of the most important class of integrity constraints can be constructed and then used for the exploitation in practical database tasks. The concept of cardinality constraints is defined, generalized and used for the simplification of the design, for the improvement of maintenance programs and for the detection of problematic design decisions.