A Cubic-Time Parsable, Lexicalized Normal Form For Context-Free Grammar That Preserves Tree Structure

Lexicalized context-free grammar (LCFG) is a tree-based formalism that makes use of both tree substitution and a restricted form of tree adjunction. Because of its use of adjunction, LCFG allows su cient freedom in the way derivations can be performed that lexicalization of context-free grammars (CFGs) is possible while preserving the structure of the trees derived by the CFGs. However, the tree adjunction permitted is su ciently restricted that LCFGs are string-wise equivalent to CFGs and have the same cubic-time worst-case complexity bounds for recognition and parsing. Submitted to Computational Linguistics This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonpro t educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories of Cambridge, Massachusetts; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories. All rights reserved. Copyright c Mitsubishi Electric Research Laboratories, 1993 201 Broadway, Cambridge, Massachusetts 02139 Publication History:{ 1. First printing, MTR 93-04 June, 1993