Dependency parsing schemata and mildly non-projective dependency parsing

  • Authors:
  • Carlos Gómez-Rodríguez;John Carroll;David Weir

  • Affiliations:
  • Universidade da Coruña, Spain;University of Sussex, UK;University of Sussex, UK

  • Venue:
  • Computational Linguistics
  • Year:
  • 2011

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Abstract

We introduce dependency parsing schemata, a formal framework based on Sikkel's parsing schemata for constituency parsers, which can be used to describe, analyze, and compare dependency parsing algorithms. We use this framework to describe several well-known projective and non-projective dependency parsers, build correctness proofs, and establish formal relationships between them. We then use the framework to define new polynomial-time parsing algorithms for various mildly non-projective dependency formalisms, including well-nested structures with their gap degree bounded by a constant k in time O(n5+2k), and a new class that includes all gap degree k structures present in several natural language treebanks (which we call mildly ill-nested structures for gap degree k) in time O(n4+3k). Finally, we illustrate how the parsing schema framework can be applied to Link Grammar, a dependency-related formalism.