Dependencies and generalized relations

A combinatorial, data-oriented approach is suggested to study generalized relational databases (GRDs) and generalized functional dependencies (GFDs). GRDs, as defined here, extend the traditional relational model by Codd. Also, certain aspects of nonfirst-normal-form databases and databases with null values can be captured in the setting of GRDs. We show that, after a suitable transformation, GFDs can be described in the framework of traditional functional dependencies (FDs). This leads to a convenient description of GFDs in terms of propositional logic.