Parsing French with Tree Adjoining Grammar: some linguistic accounts

Parsing French with Tree Adjoining Grammar: some linguistic accounts Anne ABEILLE* Department of Computer and Information Science University of Pennsylvania Philadelphia PA 19104-6389 USA Abstract We present the first sizable grammar written for TAG. We present the linguistic coverage of our grammar, and explain the linguistic reasons which lead us to choose the particular representations. We show that TAG formal- ism provides sufficient constraints for handling most of the linguistic phenomena, with minimal linguistic stipula- tions. We first state the basic structures needed for pars- ing French, with a particular emphasis on TAG's extended domain of locality that enables us to state complex sub- categorizaeion phenomena in a natural way. We then give a detailed analysis of sentential complements, because it has lead us to introduce substitution in the formalism, and because TAG makes interesting predictions. We dis- cuss the different linguistic phenomena corresponding to adjunction and to substitution respectively. We then movc on to support verb constructions, which are represented in a TAG in a simpler way than the usual double analysis. It is the first time support verb constructions are handled in a parser. We lastly give an overview of the treatment of adverbs, and suggest a treatment of idioms which make them fall into the same representations as 'free' structures. Introduction Tree Adjoining Grammar (TAG) was introduced by/Joshi et al. 1975/ as a formalism for linguistic description. A TAG's basic component is a finite set of elementary trees, each of which is a domain of locality, and can be viewed as a minimal linguistic structure. A TAG comprises of two kinds of elementary trees: initial trees (a), which are complete structures, usually rooted in S, with preterminals on all their leaves, and aux- iliary trees (fl), which are constrained to have exactly one leaf node labeled with a non-terminal of the same cate- gory as their root node. We have added lexical trees (6), which are initial trees corresponding to arguments. Their insertion in preterminal nodes of elementary trees, which serves as psedicates, is obligatory. Sentences of the language of a TAG are derived from the composition of an initial tree and any number of auxiliary trees by an operation called 'adjunction'. Adjunction in- *Visiting from University of Paris VII. This work was partially supported by a J. W. Zellidja grant, and also by ARO grant DAA29-84-9-007, DARPA grant N0014-85-K0018, NSF grants MGS- 82-191169 slid DCR-84-10413 to the University of Pennsylvania. Thanks are due to Aravind Joshl, Anthony Kroch, and Yves Schahes. serts an auxiliary tree at one of the corresponding nodes of an elementary or a derived tree. Recursion is provided by the structure of the auxiliary trees which can adjoin into themselves. Adjunction allows the insertion of a complete structure at an interior node of another complete struc- ture. It appears to be a natural way of handling adverbs and modifiers in natural language. Three constraints can be associated to any node of an elementary tree : null adjunction (NA), obligatory adjunction (OA), and selec- …

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