Hierarchical search for parsing

  • Authors:
  • Adam Pauls;Dan Klein

  • Affiliations:
  • University of California at Berkeley, Berkeley, CA;University of California at Berkeley, Berkeley, CA

  • Venue:
  • NAACL '09 Proceedings of Human Language Technologies: The 2009 Annual Conference of the North American Chapter of the Association for Computational Linguistics
  • Year:
  • 2009

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Abstract

Both coarse-to-fine and A* parsing use simple grammars to guide search in complex ones. We compare the two approaches in a common, agenda-based framework, demonstrating the tradeoffs and relative strengths of each method. Overall, coarse-to-fine is much faster for moderate levels of search errors, but below a certain threshold A* is superior. In addition, we present the first experiments on hierarchical A* parsing, in which computation of heuristics is itself guided by meta-heuristics. Multi-level hierarchies are helpful in both approaches, but are more effective in the coarse-to-fine case because of accumulated slack in A* heuristics.