A New Category of Relations: Combinationally Constrained Relations


Department of Electrical & Computer Engineering,Sharif University of Technology


Abstract. The normalization theory in relational database design is a classical subject investigated
in di erent papers. The results of these research works are the stronger normal forms such as 5NF,
DKNF and 6NF. In these normal forms, there are less anomalies and redundancies, but it does not mean
that these stronger normal forms are free of anomalies and redundancies. Each normal form discussion
is based on a particular constraint. In this paper, we introduce relations which contain a new kind of
constraint called combinational constraint". We distinguish two important kinds of this constraints,
namely Strong and Weak. Also we classify the Combinationally Constrained Relations as Single and
Multiple. We introduce all kinds of such relations and specify them using their quantitative properties,
formally. It can be shown that these relations are in 5NF or 6NF and still they contain redundancies and
have some anomalies.