An empirical study of semi-supervised structured conditional models for dependency parsing

  • Authors:
  • Jun Suzuki;Hideki Isozaki;Xavier Carreras;Michael Collins

  • Affiliations:
  • NTT Corp., Kyoto, Japan;NTT Corp., Kyoto, Japan;MIT CSAIL, Cambridge, MA;MIT CSAIL, Cambridge, MA

  • Venue:
  • EMNLP '09 Proceedings of the 2009 Conference on Empirical Methods in Natural Language Processing: Volume 2 - Volume 2
  • Year:
  • 2009

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Abstract

This paper describes an empirical study of high-performance dependency parsers based on a semi-supervised learning approach. We describe an extension of semi-supervised structured conditional models (SS-SCMs) to the dependency parsing problem, whose framework is originally proposed in (Suzuki and Isozaki, 2008). Moreover, we introduce two extensions related to dependency parsing: The first extension is to combine SS-SCMs with another semi-supervised approach, described in (Koo et al., 2008). The second extension is to apply the approach to second-order parsing models, such as those described in (Carreras, 2007), using a two-stage semi-supervised learning approach. We demonstrate the effectiveness of our proposed methods on dependency parsing experiments using two widely used test collections: the Penn Treebank for English, and the Prague Dependency Tree-bank for Czech. Our best results on test data in the above datasets achieve 93.79% parent-prediction accuracy for English, and 88.05% for Czech.