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<Paper uid="C88-1002">
  <Title>Parsing French with Tree Adjoining Grammar: some linguistic accounts</Title>
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Abstract
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    <Paragraph position="0"> We present the first sizable grammar written for TAG.</Paragraph>
    <Paragraph position="1"> 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 formalism provides sufficient constraints for handling most of the linguistic phenomena, with minimal linguistic stipulations. We first state the basic structures needed for parsing French, with a particular emphasis on TAG's extended domain of locality that enables us to state complex subcategorizaeion 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 discuss 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.</Paragraph>
    <Paragraph position="2"> 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.</Paragraph>
    <Paragraph position="3"> 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.</Paragraph>
    <Paragraph position="4"> 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 auxiliary trees (fl), which are constrained to have exactly one leaf node labeled with a non-terminal of the same category 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.</Paragraph>
    <Paragraph position="5"> 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 MGS82-191169 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 structure. 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 selective adjunction (SA). Because of the formal properties of adjunction, the formalism is more powerful them Context-I~ee Gran~nar, .but only mildly so/Joshi 85/. Most of its linguistic properties come from the fact that it factors recursion from local dependencies. We are thus able to localize all dependencies such as subcategorization, agreement, and filler-gap relations. Because trees, and not categories, are considered ms the units of the grammar, TAGs have a broader domain of locality than usual phrase structure rules.</Paragraph>
    <Paragraph position="6"> We have added substitution to the formalism, essentially for descriptive purposes. Although adjunction is more powerful than substitution, and could be used to simulate it, it seems more natural to have substitution itself for lexical insertion and for constructions in which the extra power of adjunction is not needed (section 2). We define a restrictive use of substitution: it inserts an initial tree (or a tree derived from an initial tree), or a lexieal tree, into an elementary tree. Substitution is always obligatory and only one constraint, selectional substitution, is defined. This improves the descriptive power of the formalism without changing its generative capacity.</Paragraph>
    <Paragraph position="7"> Features structures can be associated with each node of an elementary tree /Vijay-Shanker 87/. They permit the dynamic assignment of constraints. Features are also used for constraining the lexieal insertion of items such as prepositions in verbal complements, coinplementizer of sentential complement or determiner in NP.</Paragraph>
    <Paragraph position="8"> Our grammar currently covers the major basic and derived constructions, such as wh-question, relativization or cleft-extraction. We are also able to handle neutral and reciprocal verbs, middle and locative alternations , as well as argument reordering such as scrambling or heavy-NP shift. We refer the reader to /Abeilld 88b/ for a more complete presentation of the grammar. In this paper, we focus on some constructions which are of particular linguistic significance.</Paragraph>
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