A Value-propagating Transformation Technique for Datalog Programs Based on Non-Deterministic Constructs

Article type: Research Article

Authors: Potikas, Petros | Rondogiannis, Panos | Gergatsoulis, Manolis

Affiliations: Computer Science Division, Department of Electrical and Computer Engineering, National Technical University of Athens, 157 73 Zografou, Athens, Greece. E-mail: [email protected] | Department of Informatics & Telecommunications, University of Athens, Panepistimiopolis, 157 84 Athens, Greece. E-mail: [email protected] | Department of Archive and Library Sciences, Ionian University, Palea Anaktora, Plateia Eleftherias, 49100 Corfu, Greece. E-mail: [email protected]

Abstract: The branching-time transformation is a recent technique for optimizing Chain Datalog programs. In this paper we propose a significant extension of the branching-time transformation which we believe opens up a promising new direction of research in the area of value-propagating Datalog optimizations. More specifically, the proposed transformation can handle more general programs that allow multiple consumptive occurrences of variables in the bodies of clauses. This extension is achieved by using as target language the temporal logic programming formalism Datalog_{nS} enriched with choice predicates (a non-deterministic construct that was originally introduced in the area of intensional logic programming). We demonstrate the correctness of the transformation and propose several optimizations that can be applied to the target code. Moreover, we define a bottom-up proof procedure that applies to the target programs and demonstrate that it always terminates (despite the fact that the Herbrand base of these programs is generally infinite).

Keywords: Logic Programming, Deductive Databases, Program and Query Transformations, Non-deterministic Constructs

Journal: Fundamenta Informaticae, vol. 72, no. 4, pp. 485-527, 2006