A constructive view of GPSG or how to make it work

Abstract

Using the formalism of generalized phrase structure grammar (GF~SG) in an NL system (e.g. for machine translation (MT)) is promising since the modular structure of the formalism is very well suited to meet some particular needs of MT. However, it seems impossible to implement GPSG in its 1985 version straightforwardly. This would involve a vast overgeneration of structures as well as processes to filter out everything but the admissible tree(s). We therefore argue for a constructive version of GPSG where information is gathered in subsequent steps to produce syntactic structures. As a result, we consider it necessary to incorporate procedural aspects into the formalism in order to use it as a linguistic basis for NL parsing and generation. The paper discusses the major implications of such a modified view of GPSG. 1

Structure-driven generation from separate semantic representations

“…A STRUCTURE-DRIVEN GENERATOR The generator to be described in this section is a module of the Berlin MT system [llauenschild/Busemann 1988], which translates sentences taken from administrative texts in an EC corpus from German into English and vicc versa. 4 The syntax formalism Used is a constructive version of GPSG [Gazdar et al 1985] as described in [Busemann/Hauenschild 1988]. The semantic representation language FAS (Functor-Argument Stuctures) [Mahr/Umbach 1990] is employed as an interface between three different processes: it is the target of GPSG-based analysis, for sentence-semantic transfer, and as the source for GPSG-based generation.…”

“…4 The syntax formalism Used is a constructive version of GPSG [Gazdar et al 1985] as described in [Busemann/Hauenschild 1988]. The semantic representation language FAS (Functor-Argument Stuctures) [Mahr/Umbach 1990] is employed as an interface between three different processes: it is the target of GPSG-based analysis, for sentence-semantic transfer, and as the source for GPSG-based generation.…”

GPSG parsing, bidirectional charts, and connection graphs

“…Thus the category of a new edge is always an extension of the category of an already existing edge (I) or of the category in the left-hand side (LHS) of an ID ale (2). Since the whole process is initialized by extending lexical inactive edges, the only categories possible for non-lexical edges are extensions of ale LHSs.…”

“…The last class of methods [2,12] try to take GPSG as it is and to design a parsing algorithin wtfich is not only sound but 'also complete with re-. spect to the theory.…”