tailieunhanh - Báo cáo khoa học: "A Deductive Approach to Dependency Parsing∗"

We define a new formalism, based on Sikkel’s parsing schemata for constituency parsers, that can be used to describe, analyze and compare dependency parsing algorithms. This abstraction allows us to establish clear relations between several existing projective dependency parsers and prove their correctness. | A Deductive Approach to Dependency Parsing Carlos Gomez-Rodriguez Departamento de Computation Universidade da Coruna Spain cgomezr@ John Carroll and David Weir Department of Informatics University of Sussex United Kingdom johnca davidw @ Abstract We define a new formalism based on Sikkel s parsing schemata for constituency parsers that can be used to describe analyze and compare dependency parsing algorithms. This abstraction allows us to establish clear relations between several existing projective dependency parsers and prove their correctness. 1 Introduction Dependency parsing consists of finding the structure of a sentence as expressed by a set of directed links dependencies between words. This is an alternative to constituency parsing which tries to find a division of the sentence into segments constituents which are then broken up into smaller constituents. Dependency structures directly show head-modifier and head-complement relationships which form the basis of predicate argument structure but are not represented explicitly in constituency trees while providing a representation in which no non-lexical nodes have to be postulated by the parser. In addition to this some dependency parsers are able to represent non-projective structures which is an important feature when parsing free word order languages in which discontinuous constituents are common. The formalism of parsing schemata Sikkel 1997 is a useful tool for the study of constituency parsers since it provides formal high-level descriptions of parsing algorithms that can be used to prove their formal properties such as correctness establish relations between them derive new parsers from existing ones and obtain efficient implementations automatically Gomez-Rodriguez et al. 2007 . The formalism was initially defined for context-free grammars and later applied to other constituencybased formalisms such as tree-adjoining grammars Partially supported by Ministerio de Educacion y Ciencia .

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