A Simple Scheme for Implementing Tabled Logic Programming Systems Based on Dynamic Reordering of Alternatives

Abstract

Tabled logic programming (LP) systems have been applied to elegantly and quickly solving very complex problems (e.g., model checking). However, techniquescurren tly employed for incorporating tabling in an existing LP system are quite complex and require considerable change to the LP system. We present a simple technique for incorporating tabling in existing LP systems based on dynamically reordering clauses containing variant callsat run-time. Our simple technique allows tabled evaluation to be performed with a single SLD tree and without the use of complex operations such as freezing of stacks and heap. It can be incorporated in an existing logic programming system with a small amount of effort. Our scheme also facilitates exploitation of parallelism from tabled LP systems. Results of incorporating our scheme in the commercial ALS Prolog system are reported.