This document discusses and compares several different probabilistic models for sequence labeling tasks, including Hidden Markov Models (HMMs), Maximum Entropy Markov Models (MEMMs), and Conditional Random Fields (CRFs).
It provides mathematical formulations of HMMs, describing how to calculate the most likely label sequence using the Viterbi algorithm. It then introduces MEMMs, which address some limitations of HMMs by incorporating arbitrary, overlapping features. CRFs are presented as an improvement over MEMMs that models the conditional probability of labels given observations, avoiding the label bias problem of MEMMs. The document concludes by describing how to train CRF models using generalized iterative scaling.
This document discusses and compares several different probabilistic models for sequence labeling tasks, including Hidden Markov Models (HMMs), Maximum Entropy Markov Models (MEMMs), and Conditional Random Fields (CRFs).
It provides mathematical formulations of HMMs, describing how to calculate the most likely label sequence using the Viterbi algorithm. It then introduces MEMMs, which address some limitations of HMMs by incorporating arbitrary, overlapping features. CRFs are presented as an improvement over MEMMs that models the conditional probability of labels given observations, avoiding the label bias problem of MEMMs. The document concludes by describing how to train CRF models using generalized iterative scaling.
2. Two Knives Cut Better Than One: Chinese Word
Segmentation with Dual Decomposition
二つのナイフでよりよく切れる:
双対分解による中国語の単語分割
http://nlp.stanford.edu/pubs/cws_wang_acl14.pdf
論文紹介
6. ラベル:単語の開始なのか、それとも中間・末尾なのか
才 能
(START)(NOTSTART)
ビタビアルゴリズムにより
確率が最も高いラベル列を探し出す
参考文献
Peng, Fuchun, Fangfang Feng and Andrew McCallum. 2004.
Chinese segmentation and new word detection using conditional
random fields. In COLING 2004.
文字に基づくモデル
12. 双対分解法の推論により変形すると
二つのより簡単な最大化問題になる
参考文献
Alexander M. Rush and Michael Collins. 2012. A tutorial on dual
decomposition and Lagrangian relaxation for inference in natural
language processing. JAIR, 45:305–362.
双対分解(Dual Decomposition)