Fundamenta Informaticae XXX (200X) 1–30 1 IOS Press Comparing and Mining Conjunctive Queries from a Relational Table with Functional Dependencies

Abstract. In this paper we study the problem of mining all frequent queries in a relational table, a problem known to be intractable even for conjunctive queries. We restrict our attention to projection-selection queries and we assume that the table to be mined satisfies a set of functional dependencies. Under these assumptions, we define two pre-orderings with respect to which the support measure is shown to be anti-monotonic. Each of these pre-orderings induces an equivalence relation for which all queries of the same equivalence class have the same support. The goal of this paper is not to provide algorithms for the computation of frequent queries, but rather to provide basic properties of pre-orderings and their associated equivalence relations showing that functional dependencies can be used for optimized computation of frequent queries. In particular, we show that one of the two pre-orderings characterizes anti-monotonicity of the support, while the other one refines the former, but allows to characterize anti-monotonicity with respect to a given table, only. Basic computational implications of these properties are discussed in the paper, based on our previous work [14]