Russell, G., A. Ballim, J. Carroll and S. Warwick-Armstrong (1993) `A practical approach to multiple default inheritance for unification-based lexicons'. In E. Briscoe, V. de Paiva and A. Copestake (eds.), Inheritance, Defaults and the Lexicon, Cambridge University Press. 137-147.
Natural language lexicons form an obvious application for techniques involving
default inheritance developed for knowledge representation in artificial
intelligence (AI). Many of the schemes that have been proposed are
highly complex - simple tree-form taxonomies are thought to be inadequate,
and a variety of additional mechanisms are employed. As Touretzky et al.
(1987) show, the intuitions underlying the behaviour of such systems may be
unstable, and in the general case they are intractable (Selman and Levesque, 1989).
It is an open question whether the lexicon requires this level of sophistication
- by sacrificing some of the power of a general inheritance system one may arrive
at a simpler, more restricted, version, which is nevertheless sufficiently
expressive for the domain. The particular context within which the lexicon
described here has been devised seems to permit further reductions in
complexity. It has been implemented as part of the ELU unification grammar
development environment for research in machine translation, comprising
parser, generator, lexicon, and transfer mechanism.