Recycling Computed Answers in Rewrite Systems for Abduction

Abstract

In rule-based systems, goal-oriented computations correspond naturally to the possible ways that an observation may be explained. In some applications, we need to compute explanations for a series of observations with the same domain. The question arises as to whether previously computed answers can be recycled. A “yes” answer could result in substantial savings of repeated computations. For systems based on classical logic, the answer is yes. For nonmonotonic systems, however, one tends to believe that the answer should be no, since recycling is a form of adding information. In this article, we show that computed answers can always be recycled, in a nontrivial way, for the class of rewrite procedures proposed earlier by the authors for logic programs with negation. We present some experimental results on an encoding of the logistics domain.