A Simple Characterization of Database Dependency Implication

Functional dependencies [4] and multivalued dependencies [5,11] are important, widely-studied constraints on databases. A fundamental issue in database theory is the question of determining whether or not a given set of dependencies (in our case, functional and multivalued dependencies) logically implies another given dependency. We provide a simple and elegant set-theoretic characterization for dependency implication. The characterization has found several applications by the first author [6-91. By making use of a theorem of Sagiv et al. [lo], we give a simple proof of the characterization.