  This paper shows how DATR, a widely used formal language for lexical
knowledge representation, can be used to define an LTAG lexicon as an
inheritance hierarchy with internal lexical rules. A bottom-up featural
encoding is used for LTAG trees and this allows lexical rules to be implemented
as covariation constraints within feature structures. Such an approach
eliminates the considerable redundancy otherwise associated with an LTAG
lexicon.
