TAILIEUCHUNG - Báo cáo khoa học: "Getting the Most out of Transition-based Dependency Parsing"

This paper suggests two ways of improving transition-based, non-projective dependency parsing. First, we add a transition to an existing non-projective parsing algorithm, so it can perform either projective or non-projective parsing as needed. Second, we present a bootstrapping technique that narrows down discrepancies between gold-standard and automatic parses used as features. | Getting the Most out of Transition-based Dependency Parsing Jinho D. Choi Department of Computer Science University of Colorado at Boulder choijd@ Martha Palmer Department of Linguistics University of Colorado at Boulder mpalmer@ Abstract This paper suggests two ways of improving transition-based non-projective dependency parsing. First we add a transition to an existing non-projective parsing algorithm so it can perform either projective or non-projective parsing as needed. Second we present a bootstrapping technique that narrows down discrepancies between gold-standard and automatic parses used as features. The new addition to the algorithm shows a clear advantage in parsing speed. The bootstrapping technique gives a significant improvement to parsing accuracy showing near state-of-the-art performance with respect to other parsing approaches evaluated on the same data set. 1 Introduction Dependency parsing has recently gained considerable interest because it is simple and fast yet provides useful information for many NLP tasks Shen et al. 2008 Councill et al. 2010 . There are two main dependency parsing approaches Nivre and McDonald 2008 . One is a transition-based approach that greedily searches for local optima highest scoring transitions and uses parse history as features to predict the next transition Nivre 2003 . The other is a graph-based approach that searches for a global optimum highest scoring tree from a complete graph in which vertices represent word tokens and edges directed and weighted represent dependency relations McDonald et al. 2005 . Lately the usefulness of the transition-based approach has drawn more attention because it generally performs noticeably faster than the graph-based 687 approach Cer et al. 2010 . The transition-based approach has a worst-case parsing complexity of O n for projective and O n1 2 for non-projective parsing Nivre 2008 . The complexity is lower for projective parsing because it can .

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