Dependency parsing with undirected graphs

  • Authors:
  • Carlos Gómez-Rodríguez;Daniel Fernández-González

  • Affiliations:
  • Universidade da Coruña Campus de Elviña, A Coruña, Spain;Universidade de Vigo Campus As Lagoas, Ourense, Spain

  • Venue:
  • EACL '12 Proceedings of the 13th Conference of the European Chapter of the Association for Computational Linguistics
  • Year:
  • 2012

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Abstract

We introduce a new approach to transition-based dependency parsing in which the parser does not directly construct a dependency structure, but rather an undirected graph, which is then converted into a directed dependency tree in a post-processing step. This alleviates error propagation, since undirected parsers do not need to observe the single-head constraint. Undirected parsers can be obtained by simplifying existing transition-based parsers satisfying certain conditions. We apply this approach to obtain undirected variants of the planar and 2-planar parsers and of Covington's non-projective parser. We perform experiments on several datasets from the CoNLL-X shared task, showing that these variants outperform the original directed algorithms in most of the cases.