Implicational Dependency Families Possessing Finite Armstrong Relations.

摘要

Let X not equal to phi be a finite collection of nonempty relations over the relation scheme R(A1, A2...,An); then the closure of X under embedding and direct product (up to isomorphism) is a finitely generated Implicational Dependency family (ID-family) generated by X. In this paper, we show that the class of finitely generated ID-families is identical to the class of those ID-families which possess a finite Armstrong relation. (KR)