A simple proof on the decidability of equivalence between recursive and nonrecursive Datalog programs

Abstract

A higher-order query language of Horn-clause programs without function symbols, also known as Datalog, has received considerable attention recently. One way to optimize Datalog programs is to transform a Datalog program into a equivalent one that can be evaluated more efficiently. Therefore, determining equivalence of Datalog programs, especially between a given recursive program and a given nonrecursive one, is a fundamental problem. We introduce a new approach to prove the decidability of this equivalence problem, by enumerating databases and using some other simple known results.