On Applying Program Transformation to Implement Suspension-Based Tabling in Prolog

Abstract

Tabling is a technique of resolution that overcomes some limitations of traditional Prolog systems in dealing with redundant sub-computations and recursion. We can distinguish two main categories of tabling mechanisms: suspension-based tabling mechanisms and linear tabling mechanisms. Suspension-based tabling mechanisms need to preserve the state of suspended tabled subgoals in order to ensure that all answers are correctly computed. A tabled evaluation can be seen as a sequence of sub-computations that suspend and later resume. On the other hand, linear tabling mechanisms use iterative computations of tabled subgoals to compute fix-points. The main idea of linear tabling is to maintain a single execution tree where tabled subgoals always extend the current computation without requiring suspension and resumption of sub-computations.