A practical implementation of DCGs

Abstract

Definite clause grammars (DCGs) are a logic counterpart to context-free grammars, the most widely-used formalism for defining the syntax of languages. The conventional implementation strategy of DCGs is translation into the logic programming language Prolog, giving rise to a parser for the defined language. This translation can be carried out in a rather straightforward way, and that is why DCGs are provided as an enhancement in a number of Prolog systems. Definite clause grammars were originally presented in [PeW80] as a formalism for describing natural languages. The implementation method presented there (and adopted as such in the Prolog systems) thus takes into account the most general structure of natural languages and produces a parser which is inherently nondeterministic.