tailieunhanh - Báo cáo khoa học: "TAG's as a Grammatical Formalism for Ceneration"

The theoretic~ apparatus of a T A G cons/sin of a primitive~ defined set of "elememary" phrase s m g n u ~ gge~ a Jqinkins'~ l'~lgJOgl thag ~ ~ ~ to d e ~ e dependency relations between two nodes within an elemeutary tree, and an "adjunction" operarlon that combines trees under specifiable constraints. The elementary frees are divided into gwo sets: initLll and auxiliary. | TAG S as a Grammatical Formalism for Generation David D. McDonald and James D. Pustejovsky Department of Computer and Information Science University of Massachusetts at Amherst 1. Abstract 2. Tree Adjunction Grammars Tree Adjoining Grammars or TAG S Joshi Levy A Takahashi 1975 Joshi 1983 Kxoch A Joshi 1985 were developed as an alternative to the standard syntactic formalisms that are used in theoretical analyses of language. They are attractive because they may provide just the aspects of context sensitive expressive power that actually appear in human languages while otherwise remaining context free. This paper describes how we have applied the theory of Tree Adjoining Grammars to natural language generation. We have been attracted to TAG S because their central operation the extension of an initial phrase structure tree through the inclusion at very specifically constrained locations of one or more auxiliary trees conerponds directly to certain central operations of our own performance-oriented theory. We begin by briefly describing TAG S as a formalism tor phrase structure tn a competence theory and summarize the points in the theory of TAG S that are germaine to our own theory. We then consider generally the position of a grammar within the generation process introducing our use of TAG S through a contrast with how others have used systemic grammars. This takes US to the core results of our paper using examples from our research with well-written texts from newspapers we walk through cur TAG inspired treatments ci raising and wh-movement and show the correspondence of the TAG adjunction operation and our attachment process. In the final section we discuss extensions to the theory motivated by the way we use the operation corresponding to TAG S adjunction in performance. This suggests that the competence theory of TAG S can be profitably projected to structures at the morphological level as well as the present syntactic level. The theoretical apparatus of a TAG