Implication of Functional Dependencies for Recursive Queries

After two decades of research in Deductive Databases, SQL99 [12] brings them again to the foreground given that SQL99 includes queries with linear recursion. Therefore some of the problems solved for the relational model demand our attention again.In this paper, we tackle the implication of functional dependencies (also known as the FD-FD implication problem) in the deductive model framework. The problem is as follows. GivenP, F, andf, wherePis a Datalog program, Fis a set of functional dependencies defined on the predicates of P, andfis a fd defined over the predicates of P, is it true that for all databasesddefined exclusively on the extensional predicates ofP, dsatisfies Fimplies that P(d) –the output database– satisfies f. Unlike the implication problem of functional dependencies in the relational data model, this problem is undecidable for general Datalog programs.In this paper, we provide two methods to check if a given set of fds will be satisfied by the output database (without computing such database) for a class of Datalog programs.