Multilayer sequence labeling

  • Authors:
  • Ai Azuma;Yuji Matsumoto

  • Affiliations:
  • Nara Institute of Science and Technology, Ikoma, Nara, Japan;Nara Institute of Science and Technology, Ikoma, Nara, Japan

  • Venue:
  • EMNLP '11 Proceedings of the Conference on Empirical Methods in Natural Language Processing
  • Year:
  • 2011

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Abstract

In this paper, we describe a novel approach to cascaded learning and inference on sequences. We propose a weakly joint learning model on cascaded inference on sequences, called multilayer sequence labeling. In this model, inference on sequences is modeled as cascaded decision. However, the decision on a sequence labeling sequel to other decisions utilizes the features on the preceding results as marginalized by the probabilistic models on them. It is not novel itself, but our idea central to this paper is that the probabilistic models on succeeding labeling are viewed as indirectly depending on the probabilistic models on preceding analyses. We also propose two types of efficient dynamic programming which are required in the gradient-based optimization of an objective function. One of the dynamic programming algorithms resembles back propagation algorithm for multilayer feed-forward neural networks. The other is a generalized version of the forward-backward algorithm. We also report experiments of cascaded part-of-speech tagging and chunking of English sentences and show effectiveness of the proposed method.