Slr Inference : an Inference Systemfor Fixed - Mode Logic Programs , Based on Slr

Deenite-clause grammars (DCGs) generalize context-free grammars in such a way that Prolog can be used as a parser in the presence of context-sensitive information. Prolog's proof procedure, however, is based on back-tracking, which may be a source of ineeciency. Parsers for context-free grammars which use backtracking, for instance, were soon replaced by more eecient methods such as LR parsers. This suggests incorporating the principles underlying LR parsing into a parser for grammars with context-sensitive information. We present a technique which applies a transformation to the program/grammar by adding leaves to the proof/parse trees and placing the contextual information in such leaves. An inference system is then easily obtained from an LR parser, since only the parts dealing with terminals (which appear at the leaves) must be modiied. Although our method is restricted to programs with xed modes, it may be preferable to DCGs under Prolog for some programs.