Pruning Search Space For Parsing Free Coordination In Categorial Grammar

Abstract

The standard resource sensitive invariants of categorial grammar are not suited to prune search space in the presence of coordination. We propose a weaker variant of count invariancy in order to prune the search space for parsing coordinated sentences at a stage prior to proper parsing. This Coordinative Count Invariant is argued to be the strongest possible instrument to prune search space for parsing coordination in categorial grammar. Its mode of operation is explained, and its effect at pruning search space is exemplified. 1 1 Lexical Ambiguity and Natural Language Parsing Lexical ambiguity is known to be a major threat to efficient parsing of natural language. It is easy to see why. Let G NL be a grammar for a language NL, and L a lexicon with initial assignment A of nonterminals to the words of NL. Let S = w 1 ... w n be a sentence over L. Under a parsing-as-deductionapproach, then, the parsing problem for S is whether for some sequence C = c 1 ... c n , with c Î A(w ), C is der..