Lexicalized TAGs, parsing and lexicons

• Authors: Anne Abeille
• Venue: HLT '89 Proceedings of the workshop on Speech and Natural Language
• Year: 1989

In our approach, each elementary structure is systematically associated with a lexical head. These structures specify extended domains of locality (as compared to a context-free grammar) over which constraints can be stated. These constraints either hold within the elementary structure itself or specify what other structures can be composed with a given elementary structure. The 'grammar' consists of a lexicon where each lexical item is associated with a finite number of structures for which that item is the head. There are no separate grammar rules. There are, of course, 'rules' which tell us how these structures are composed. A grammar of this form will be said to be 'lexicalized'. A 'lexicalized' grammar naturally follows from the extended domain of locality of TAGs.A general parsing strategy for 'lexicalized' grammars is discussed. In the first stage, the parser selects a set of elementary structures associated with the lexical items in the input sentence, and in the second stage the sentence is parsed with respect to this set. An Earley-type parser for TAGs has been has been developed. It can be adapted to take advantage of the two steps parsing strategy. The system parses unification formalisms that have a CFG skeleton and that have a TAG skeleton.Along with the development of an Earley-type parser for TAGs, lexicons for English are under development. A lexicons for French is also being developed. Subsets of these lexicons are being incrementally interfaced to the parser.We finally show how idioms are represented in lexicalized TAGs. We assign them regular syntactic structures while representing them semantically as one entry. We finally show how they can be parsed by a parsing strategy as mentioned above.