TAILIEUCHUNG - Báo cáo khoa học: "Guided Parsing of Range Concatenation Languages"

The theoretical study of the range concatenation grammar [RCG] formalism has revealed many attractive properties which may be used in NLP. In particular, range concatenation languages [RCL] can be parsed in polynomial time and many classical grammatical formalisms can be translated into equivalent RCGs without increasing their worst-case parsing time complexity. For example, after translation into an equivalent RCG, any tree adjoining grammar can be parsed in time. | Guided Parsing of Range Concatenation Languages Francois Barthelemy Pierre Boullier Philippe Deschamp and Eric de la Clergerie INRIA-Rocquencourt Domaine de Voluceau 105 78153 Le Chesnay Cedex France @ Abstract The theoretical study of the range concatenation grammar RCG formalism has revealed many attractive properties which may be used in NLP. In particular range concatenation languages RCL can be parsed in polynomial time and many classical grammatical formalisms can be translated into equivalent RCGs without increasing their worst-case parsing time complexity. For example after translation into an equivalent RCG any tree adjoining grammar can be parsed in ỡ n6 time. In this paper we study a parsing technique whose purpose is to improve the practical efficiency of RCL parsers. The non-deterministic parsing choices of the main parser for a language p are directed by a guide which uses the shared derivation forest output by a prior RCL parser for a suitable superset of L. The results of a practical evaluation of this method on a wide coverage English grammar are given. 1 Introduction Usually during a nondeterministic process when a nondeterministic choice occurs one explores all possible ways either in parallel or one after the other using a backtracking mechanism. In both cases the nondeterministic process may be assisted by another process to which it asks its way. This assistant may be either a guide or an oracle. An oracle always indicates all the good ways that will eventually lead to success and those good ways only while a guide will indicate all the good ways but may also indicate some wrong ways. In other words an oracle is a perfect guide Kay 2000 and the worst guide indicates all possible ways. Given two problems Pl and Pl and their respective solutions .5 I and 2 if they are such that Si D Sz any algorithm which solves Pl is a candidate guide for nondeterministic .

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