Detecting Unsolvable Queries for Definite Logic Programs
Abstract
In solving a query, the SLD proof procedure for definite programs sometimes searches an infinite space for a non existing solution. For example, querying a planner for an unreachable goal state. Such programs motivate the development of methods to prove the absence of a solution. Considering the definite program and the query ``<- Q'' as clauses of a first order theory, one can apply model generators which search for a finite interpretation in which the program clauses as well as the clause ``false <- Q'' are true. This paper develops a new approach which exploits the fact that all clauses are definite. It is based on a goal directed abductive search in the space of finite pre-interpretations for a pre-interpretation such that ``Q'' is false in the least model of the program based on it. Several methods for efficiently searching the space of pre-interpretations are presented. Experimental results confirm that our approach find solutions with less search than with the use of a first order model generator.
Cite
@article{arxiv.cs/0003067,
title = {Detecting Unsolvable Queries for Definite Logic Programs},
author = {Maurice Bruynooghe and Henk Vandecasteele and D. Andre de Waal and Marc Denecker},
journal= {arXiv preprint arXiv:cs/0003067},
year = {2007}
}
Comments
32 pages including appendix. A preliminary version appeared in proceedings PLILP/ALP98 (Springer LNCS 1490) This version, without appendix appeared in Journal Functional and Logic Programming 1999