On the Equivalence of Database Models

All eqmvalence is estabhshed between network databases and a subclass of relational databases. A database is a set of files together w~th a set of constraints that the fdes must satisfy. The constraints are spectfied by Bachman diagrams m the network model and by data dependencies m the relational model. The subclass of relatmnal databases of interest ~s characterized by the absence of two properties of data dependencies: conflzct and contention It is proved that network databases with loop-free Bachman diagrams are eqmvalent to relational databases which are free of conflicts and contenUons. When its Bachman dmgram has loops, a network database ts equivalent to a collection of relattonal databases in this subclass.