Reduced MVDs and minimal covers

Abstract

Multivalued dependencies (MVDs) are data dependencies that appear frequently in the “real world” and play an important role in designing relational database schemes. Given a set of MVDs to constrain a database scheme, it is desirable to obtain an equivalent set of MVDs that do not have any redundancies. In this paper we define such a set of MVDs, called reduced MVDs, and present an algorithm to obtain reduced MVDs. We also define a minimal cover of a set of MVDs, which is a set of reduced MVDs, and give an efficient method to find such a minimal cover. The significance and properties of reduced MVDs are also discussed in the context of database design (e.g., 4NF decomposition) and conflict-free MVDs.