Equivalence and Mapping of Database Schemes

We investigate the problem of database equivalence which arises in database design process. We introduce a graph formalism for the treatment of this problem. More precisely, we represent Entity-Relationship schemes by a special kind of graphs (called JFD-graphs) and we give a simple and efficient algorithm for testing the equivalence of two schemes. In addition, we present a set of elementary operators (preserving equivalence) for modifying an ,Entity-Relationship scheme and we prove that all equivalent schemes can be obtained by repeatedly applying such operators. Finally, we propose a methodology for mapping Entity-Relationship schemes into both relational and network schemes.