Parameter estimation for statistical parsing models: theory and practice of distribution-free methods

  • Authors:
  • Michael Collins

  • Affiliations:
  • MIT Computer Science and Artificial Intelligence Laboratory, Cambridge, MA

  • Venue:
  • New developments in parsing technology
  • Year:
  • 2004

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Abstract

A fundamental problem in statistical parsing is the choice of criteria and algo-algorithms used to estimate the parameters in a model. The predominant approach in computational linguistics has been to use a parametric model with some variant of maximum-likelihood estimation. The assumptions under which maximum-likelihood estimation is justified are arguably quite strong. This chapter discusses the statistical theory underlying various parameter-estimation methods, and gives algorithms which depend on alternatives to (smoothed) maximum-likelihood estimation. We first give an overview of results from statistical learning theory. We then show how important concepts from the classification literature - specifically, generalization results based on margins on training data - can be derived for parsing models. Finally, we describe parameter estimation algorithms which are motivated by these generalization bounds.