Logical Database Design with Inclusion Dependencies

Contrary to popular belief, relation schemes in good classical normal forms are not necessarily devoid of redundancies. This arises from the fact that classical data dependencies are oblivious to important constraints which may exist between sets of attributes occuring in different relation schemes. In this paper, we study how inclusion dependencies (INDs) can be used to model these constraints leading to the design of better database schemes. A new normal form, called Inclusion Normal Form (INNF), is proposed. Unlike classical normal forms, the INNF characterizes a database scheme as a whole rather than the individual relation schemes. We show that a database scheme in IN-NF is always in Improved 3NF, while the converse is not true. Finally, we demonstrate how classical relational design framework may be extended to faciliate the design of database schemes in IN-NF.