P-PATR: A Compiler for Unification-Based Grammars

Abstract : P-PATR is a compiler for unification-based grammars that is written in Quintus Prolog running on a Sun 2 workstation. P-PATR is based on the PATR-II formalism [14] developed at SRI International. PATR is a simple, unification-based formalism capable of encoding a wide variety of grammars. As a result of this versatility, several parsing systems and development environments based on this formalism have been implemented [18,5]. P-PATR is one such system, designed in response to the slow parse times of most of the other PATR implementations Most of the currently running PATR systems operate by interpreting a PATR grammar. P-PATR differs from these systems by compiling the grammar into a Prolog definite clause grammar (DCG) [8]. The compilation is done only once for a given grammar; the resulting DCG contains all the information in the original PATR grammar in a form readily conducive to parsing. The advantage of compilation is that less work needs to be done during parsing, as some of the necessary computations have already been performed in the compilation phase.