A Method for Synthesizing Normal Form Database Schemes Under Functional and Inclusion Dependencies

摘要

This paper proposes a method of synthesizing third normal form(3NF) database scheme(DS) when functional dependencies (FDs) and inclusion dependencies(INDs) both exist. When these two types of dependencies exist, synthesizing relational schemes (RSs) having no attribute transitively dependent on primely keys require us to consider the derivation of FDs by the interaction between FDs and INDs in addition to derivations of FDs alone. But, to the best of our knowledge, there is no complete derivation axioms to this interaction. Therefore we restrict our derivation rule to FD and IND proper derivation axioms and pull back rule that is one of representative sound derivation rules for interaction between FDs and INDs and define 3NF DS under this condition as Ling et al. define their 3NF DS.rnOur method have two characters as follows. One is that, on an acyclicity assumption on IND set , it deduces the problem of determining the closure of FDs and INDs to computing on each RS the closure of FD set after pull back rule is applied. The other is that, in the procedure transforming each RS into 3NF RSs, the step eliminating redundant FDs, which may be executed both before and after merging equivalent keys in Berri and Bernstein's method, is done only after merging equivalent keys.