A Constructive View of GPSG or How to Make It Work

A Constructive View of GPSG or How to Make It Work Stephan BUSEMANN Christa HAUENSCHILD Technical University of Berlin Institute for Software and Theoretical Computer Science Project Group KIT Sekr. FR 5-12 Franklinstr. 28/29 D-1000 Berlin 10 E-mail: busemann@ db0tui 11.bitnet 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 1 Introduction Any attempt to build a multi-lingual MT system as in EUROTRA [King, Perschke 1987] must provide for massive modularization in order to avoid developing 9 parsers, 9 generators and 72 transfer components for the 9 languages involved, not to mention the different but redundant formulations of linguistic knowledge embodied in them. The most obvious approach consists in developing one single parser, one single generator, and one single transfer component, the first two being capable of dealing with grammars for different languages and the latter with transfer 1 This work has been developed in the project KFr-FAST (KIT = Kilnstliche Intelligenz und Textverstehen (Artificial Intelligence and Text Understanding); FAST = Functor Argument Structure for Translation), which constitutes the Berlin component of the complementary research project of EuroWa-D. It receives grants by the Federal Minister for Research anti Technology under contract 1013211. rules for different pairs of languages. Moreover, an MT system must be based on a linguistically justified theory of grammar. This theory has to be implemented in the system, where it determines the construction of a syntactic representation of a sentence during the parsing of some input string as well as during the generation based on the output of the transfer component. The theory of GPSG (see [Gazdar et al. 1985], henceforth: [GKPS]) has been tested for its usefulness for MT [ttauenschild/Busemann 1988]. It offers the high degree of modul,'u'ity that is required. For instance, an implementation of the GPSG formalism would be able to run with different grammars, and linguistic generalizations would either evolve from the formalism (in the case of universals), or be expressible within the grammars (in the case of language- specific generalizations). We shall distinguish between the formalism and the grammar in the following way; the formalism consists of the Feature Instantiation Principles (FIPs), the formal definition of syntactic features, categories, Feature Co-occurrence Restrictions (FCRs), Immediate Dominance (ID) rules, Linear Precedence (LP) statements, admissible trees, etc. The grammars consist of …

Content truncated to 500 words