A Binding Rule for Government-binding Parsing

A Binding Rule for Government-binding Parsing Nelson CORREA IBM Thomas d. Watson Re.search Center P. O. Box 704 Yorktown lteights, NY 10598 USA Abstract In this paper I propose a Binding rule for the iden- tification of pronoun and anaphor referents in phrase-structure trees, assuming the general frame- work of lhe Government-binding theory outlined by Chom,;ky (1981). The Binding rule, specified by means of an attribute grammar, is a particular instantiation of the Free Indexing rule and binding axioms in Chomsky's Binding theory, with certain empirical and practical advantages. The complexi- ties of the Binding rule proposed, as well as that inherent in Chomsky's Binding theory, are studied, and it i~ shown that the new rule is more psychologically plausible and cornputationally effi- cient than the original theory on wtfich it is based. The fragment of the attribute grammar shown here is part of an English grammar and parser being developed in tile Prolog and PLNLP languages. Introduction Binding is a component subtheory of Government- binding which applies in the derivation of the logical form of utterances from their surface rcpre- sentation. The area of semantic interpretation dealt with by the binding theory is that of anaphora. Binding theory defines only syntactic conditions on anaphora; the reader is referred to /Hobbs, 1978/ for some of the extra-syntactic factors that might be involved. Binding assumes an Indexing rule which applies to an input S-Structure tree and annotates it, assigning to every NP node ha the input tree a referential index, which represents the coreferenee relation ot the NP with other NPs in the input. In this paper research is continued on the use of attribute grammars to provide a fully explicit and computationally oriented statement of the Governmc.nt-binding (GB) theory /Correa, 1987/. The Binding rule presented here improves over the standard statement of the Binding theory in two respects: From an empirical point of view, the new rule accounts for crossover binding phenomena /Kuno, 1987/ without recourse to reconstruction /Chomsky, 1981/; from a practical point of view, the new rule is more computationally sensible than the generate-and-test approach understood in Chomsky's theory, and hence is a plausible candi- date for incorporation in natural-language parsers that account tot anaphora. Previous literature on GB parsing /Wehrli, 1984; Sharp, 1985; Kashket, 1986; Kuhns, 1986; Abney, 1986/has not addressed the issue of implementation of the Binding theory) The present paper intends in part to fill this gap. In the development below I will assume that the reader is thmiliar with attribute grammars and the basic concepts and terminology of Government- binding, although not necessarily with the Binding theory. The reader is referred to Waite and Goos (1984) for a concise introduction to attribute gram- mars, and Sells (1985) for the basic assumptions of Government-binding. Chomsky's Binding Theol T Binding theory defines the syntactic constraints on coreferenee that exist between the noun phrases in a sentence. In the course ot" doing this, thE themy indirectly determines constraints on the distribution of certain kinds of noun phrases. …

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