Decomposition of a relation into fourth normal forms

摘要

In the relational model, various relationships may exist between the attributes in a relation. The relationships are described by functional and multivalued dependencies. The functional dependencies are the basic elements for the decomposition of a relation into a family of relations in second, third, and Boyce-Codd normal forms. The multivalued dependencies, which include the functional dependencies as a special case, extend the decomposition further into a collection of relations in fourth normal form. This paper examines the conditions under which a relation in Boyce-Codd normal form should be decomposed further into fourth normal form and a fourth normal form normalization procedure is presented.