Generalization of typed include dependencies with null values in databases

Abstract

The paper discusses a new type of dependency in databases, which is a generalization of inclusion dependencies. Traditionally, such dependencies are used in practice to ensure referential integrity. In this case, the restriction is established only between a pair of relations, the first of which is called the main, the second is external. In practice, referential integrity often needs to be established for a larger number of relations, where several main and several external relations participate in the same constraint. Such a structure corresponds to an ultragraph. The paper provides a rationale for generalized inclusion dependencies that take into account the presence of null values in external relations. Based on the study of the properties of typed dependencies, a system of axioms is obtained, for which consistency (soundness) and completeness are proved.