The lexicon is now a major focus of research in computational linguistics and natural language processing (NLP), as more linguistic theories concentrate on the lexicon and as the acquisition of an adequate vocabulary has become the chief bottleneck in developing practical NLP systems. This collection describes techniques of lexical representation within a unification-based framework and their linguistic application, concentrating on the issue of structuring the lexicon using inheritance and defaults. Topics covered include typed feature structures, default unification, lexical rules, multiple inheritance and non-monotonic reasoning. The contributions describe both theoretical results and implemented languages and systems, including DATR, the Stuttgart TFS and ISSCO's ELU. This book arose out of a workshop on default inheritance in the lexicon organized as a part of the Esprit ACQUILEX project on computational lexicography. Besides the contributed papers mentioned above, it contains a detailed description of the ACQUILEX lexical knowledge base (LKB) system and its use in the representation of lexicons extracted semi-automatically from machine-readable dictionaries.

Table of Contents:
Contributors; 1. Introduction Ted Briscoe; 2. Skeptical and credulous default unification with applications to templates and inheritance Bob Carpenter; 3. Prioritised multiple inheritance in DATR Roger Evans, Gerald Gazdar and Lionel Moser; 4. Some reflections on the conversion of the TIC lexicon into DATR Lynne J. Cahill; 5. Norms or inference tickets? a frontal collision between intuitions Michael Morreau; 6. Issues in the design of a language for representing linguistic information based on inheritance and feature structures Rémi Zajac; 7. Feature-based inheritance networks for computational lexicons Hans-Ulrich Krieger and John Nerbonne; 8. A practical approach to multiple default inheritance for unification-based lexicons Graham Russell, Afzal Ballim, John Carroll and Susan Warwick-Armstrong; 9. The ACQUILEX LKB: an introduction Ann Copestake, Antonio Sanfilippo, Ted Briscoe and Valeria de Paiva; 10. Types and constraints in the LKB Valeria de Paiva; 11. LKB encoding of lexical knowledge Antonio Sanfilippo; 12. Defaults in lexical representation Ann Copestake; 13. Untangling definition structure into knowledge representation Piek Vossen and Ann Copestake; Appendices; References; Indexes.