Feature selection for fluency ranking

  • Authors:
  • Daniël de Kok

  • Affiliations:
  • University of Groningen

  • Venue:
  • INLG '10 Proceedings of the 6th International Natural Language Generation Conference
  • Year:
  • 2010

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Abstract

Fluency rankers are used in modern sentence generation systems to pick sentences that are not just grammatical, but also fluent. It has been shown that feature-based models, such as maximum entropy models, work well for this task. Since maximum entropy models allow for incorporation of arbitrary real-valued features, it is often attractive to create very general feature templates, that create a huge number of features. To select the most discriminative features, feature selection can be applied. In this paper we compare three feature selection methods: frequency-based selection, a generalization of maximum entropy feature selection for ranking tasks with real-valued features, and a new selection method based on feature value correlation. We show that the often-used frequency-based selection performs badly compared to maximum entropy feature selection, and that models with a few hundred well-picked features are competitive to models with no feature selection applied. In the experiments described in this paper, we compressed a model of approximately 490.000 features to 1.000 features.