Experiments in Reusability of Grammatical Resources

1 Introduction Substantial formal grammatical and lexical resources exist in various NLP systems and in the form of textbook specifications. In the present paper we report on experimental results obtained in manual , semi-antomatic and automatic migration of entire computational or textbook descriptions (as opposed to a more informal reuse of ideas or the design of a single "poly-theoretic" representation) from a variety of formalisms into the ALEP formalism. 1 The choice of ALEP (a comparatively lean, typed feature structure formalism based on rewrite rules) was motivated by the assumption that the study would be most interesting if the target formalism is relatively mainstream without overt ideological commitments to particular grammatical theories. As regards the source formalisms we have attempted migrations of descriptions in HPSG (which uses fully-typed feature structures and has a strong 'non-derivational' flavour), ETS (an un-typed stratificational formalism which essentially uses rewrite rules for feature structures and has run-time non-monotonic devices) and LFG (which is an un-typed constraint and CF-PSG based formalism with extensions such as existential, negative and global well-formedness constraints). the CEC as part of the project ET10/52. Reusability of grammatical resources is an important idea. Practically, it has obvious economic benefits in allowing grammars to be developed cheaply; for the-oreticians it is important in allowing new formalisms to be tested out, quickly and in depth, by providing large-scale grammars. It is timely since substantial computational grammatical resources exist in various NLP systems, and large scale descriptions must be quickly produced if applications are to succeed. Meanwhile, in the CL community, there is a perceptible paradigm shift towards typed feature structure and constraint based systems and, if successful, migration allows such systems to be equipped with large bodies of descriptions drawn from existing resources. In principle, there are two approaches to achieving the reuse of grammatical and lexical resources. The first involves storing or developing resources in some theory neutral representation language, and is probably impossible in the current state of knowledge. In this paper, we focus on reusability through migration-the transfer of linguistic resources (grammatical and lexical descriptions) from one computational formalism into another (a target computational formalism). Migration can be completely manual (as when a linguist attempts to encode the analyses of a particular linguistic theory in some compu-tationally interpreted formalism), semi-automatic or automatic. The starting resource can be a paper description or an implemented, runnable grammar. The literature on migration is thin, …