Minimum Covers in Relational Database Model

Abstract

Numerous algonthms concernmg relahonal databases use a cover for a set of funcUonal dependencies as all or part of their input Examples are Been and Bernsteln's synthesis algorithm and the tableau modtfication algorithm of Aho et al The performance of these algorahms may depend on both the number of funcuonal dependencies m the cover and the total size of the cover Starting with a smaller cover wdl make such algorithms run faster After Bernstem, many researchers beheve that the problem of finding a minimum cover is NP- complete It as shown here that minimum covers can be found m polynomial time, using the nouon of dwect determmatwn The proofdetads the structure ofmmtmum covers, refining the structure Bernstem and Been show for nonredundant covers The kernel algorithm of Lewis, Sekino, and TIng is improved using these results