TAILIEUCHUNG - Báo cáo khoa học: "Parsing preferences with Lexicalized Tree Adjoining Grammars : exploiting the derivation tree"

Since Kimball (73) parsing preference principles such as "Right association" (RA) and "Minimal attachment" (MA) are often formulated with respect to constituent trees. We present 3 preference principles based on "derivation trees" within the framework of LTAGs. We argue they remedy some shortcomings of the former approaches and account for widely accepted heuristics (. argument/modifier, idioms.). | Parsing preferences with Lexicalized Tree Adjoining Grammars exploiting the derivation tree Alexandra KINYON TALANA Universite Paris 7 case 7003 2pl Jussieu 75005 Paris France Alexandra. Kinyon@linguist .jussieu. fr Abstract Since Kunball 73 parsing preference principles such as Right association RA and Minimal attachment MA are often formulated with respect to constituent trees. We present 3 preference principles based on derivation trees within the framework of LTAGs. We argue they remedy some shortcomings of the former approaches and account for widely accepted heuristics . argument modifier idioms. . Introduction The inherent characteristics of LTAGs . lexicalization adjunction an extended domain of locality and mildly-context sensitive power makes it attractive to Natural Language Processing LTAGs are parsable in polynomial time and allow an elegant and psycholinguistically plausible representation of natural language1 2. Large coverage grammars were developed for English Xtag group 95 and French Abeille 91 . Unfortunately large grammars yield high ambiguity rates Doran al. 94 report parses sentence on a WSJ corpus of 18730 sentences using a wide coverage English grammar. Srinivas al. 95 formulate domain independent heuristics to rank parses. But this approach is practical English-oriented not explicitly linked to psycholinguistic results and does not fully exploit derivation 1 . Frank 92 discusses the psycholinguistic relevance of adjunction for Children Language Acquisition Joshi 90 discusses psycholinguistic results on crossed and serial dependencies. information. In this paper we present 3 disambiguation principles which exploit derivation trees. 1. Brief presentation of LT AGs A LTAG consists of a finite set of elementary trees of finite depth. Each elementary tree must anchor one or more lexical item s . The principal anchor is called head other anchors are called co-heads . All leaves in elementary trees are either anchor foot node noted .

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