dependency parsing as head selection
play

Dependency Parsing as Head Selection Xingxing Zhang , Jianpeng Cheng, - PowerPoint PPT Presentation

Dependency Parsing as Head Selection Xingxing Zhang , Jianpeng Cheng, Mirella Lapata Institute for Language, Cognition and Computation University of Edinburgh x.zhang@ed.ac.uk April 6, 2017 Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency


  1. Dependency Parsing as Head Selection Xingxing Zhang , Jianpeng Cheng, Mirella Lapata Institute for Language, Cognition and Computation University of Edinburgh x.zhang@ed.ac.uk April 6, 2017 Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 1 / 18

  2. Dependency Parsing Dependency Parsing is the task of transforming a sentence S = ( root , w 1 , w 2 , . . . , w N ) into a directed tree originating out of root . Parsing Algorithms Transition-based Parsing Graph-based Parsing Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 2 / 18

  3. Dependency Parsing Dependency Parsing is the task of transforming a sentence S = ( root , w 1 , w 2 , . . . , w N ) into a directed tree originating out of root . Parsing Algorithms Transition-based Parsing Graph-based Parsing Our parser is neither Transition-based nor Graph-based (during training) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 2 / 18

  4. Transition-based Parsing Data Structure Buffer, Stack, Arc Set Parsing: Choose an action from SHIFT REDUCE-Left REDUCE-Right Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 3 / 18

  5. Graph-based Parsing A Sentence → A Directed Complete Graph (Graphs from Kubler et al., 2009) Parsing: Finding Maximum Spanning Tree Chu-Liu-Edmond algorithm (Chu and Liu, 1965) Eisner algorithm (Eisner 1996) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 4 / 18

  6. Recent Advances Mostly replacing discrete features with Neural Network features. Transition-based Parsers Feed-Forward NN features (Chen and Manning, 2014) Bi-LSTM features (Kiperwasser and Goldberg, 2016) Stack LSTM: Buffer, Stack and Action Sequences modeled by Stack-LSTMs (Dyer et al., 2015) Graph-based Parsers Tensor Decomposition features (Lei et al., 2014) Feed-Forward NN features (Pei et al., 2015) Bi-LSTM features (Kiperwasser and Goldberg, 2016) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 5 / 18

  7. Do we need a transition system or graph algorithm? root kids love candy Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 6 / 18

  8. Do we need a transition system or graph algorithm? root kids love candy An important fact: Every word has only one head! Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 6 / 18

  9. Do we need a transition system or graph algorithm? root kids love candy An important fact: Every word has only one head! Why not just learn to select the head? Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 6 / 18

  10. Dependency Parsing as Head Selection DeNSe : De pendency N eural Se lection Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 7 / 18

  11. Dependency Parsing as Head Selection DeNSe : De pendency N eural Se lection Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 7 / 18

  12. Dependency Parsing as Head Selection DeNSe : De pendency N eural Se lection Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 7 / 18

  13. Dependency Parsing as Head Selection DeNSe : De pendency N eural Se lection exp( MLP ( a root , a love )) P head ( root | love , S ) = � 3 k =0 exp( MLP ( a k , a love )) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 7 / 18

  14. Dependency Parsing as Head Selection DeNSe : De pendency N eural Se lection exp( MLP ( a root , a love )) P head ( root | love , S ) = � 3 k =0 exp( MLP ( a k , a love )) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 7 / 18

  15. Decoding Greedy Decoding: The output may not be a (projective) tree! Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 8 / 18

  16. Decoding Greedy Decoding: The output may not be a (projective) tree! Greedy Decoding Dataset #Sent (Dev) Tree Proj PTB (English) 1,700 95.1 86.6 CTB (Chinese) 803 87.0 73.1 Czech 374 87.7 65.5 German 367 96.7 67.3 Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 8 / 18

  17. Decoding Greedy Decoding: The output may not be a (projective) tree! Greedy Decoding Dataset #Sent (Dev) Tree Proj PTB (English) 1,700 95.1 86.6 CTB (Chinese) 803 87.0 73.1 Czech 374 87.7 65.5 German 367 96.7 67.3 Decoding with a Maximum Spanning Tree Algorithm (relatively rare) Projective Parsing: Eisner Algorithm Non-projective Parsing: Chu-Liu-Edmond Algorithm Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 8 / 18

  18. Labelled Parser A two-layer Rectifier Network (Glorot et al., 2011) Dependent Word: Bi-LSTM Feature Word Embedding PoS Embedding Head Word: Bi-LSTM Feature Word Embedding PoS Embedding Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 9 / 18

  19. Experiments Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 10 / 18

  20. Projective Parsing Results (PTB; English) NN (Chen & Manning, 2014); S-LSTM (Dyer et al., 2015); Bi-LSTM (Kiperwasser & Goldberg, 2016); SynNet (Andor et al. 2016) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 11 / 18

  21. Projective Parsing Results (PTB; English) NN (Chen & Manning, 2014); S-LSTM (Dyer et al., 2015); Bi-LSTM (Kiperwasser & Goldberg, 2016); SynNet (Andor et al. 2016) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 11 / 18

  22. Projective Parsing Results (PTB; English) NN (Chen & Manning, 2014); S-LSTM (Dyer et al., 2015); Bi-LSTM (Kiperwasser & Goldberg, 2016); SynNet (Andor et al. 2016) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 11 / 18

  23. Projective Parsing Results (PTB; Chinese) NN (Chen & Manning, 2014); S-LSTM (Dyer et al., 2015); Bi-LSTM (Kiperwasser & Goldberg, 2016); 3rd-cubic (Zhang & McDonald 2014) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 12 / 18

  24. Non-projective Parsing Results (German) MST-1st, MST-2nd (McDonald et al., 2005) Turbo-1st, Turbo-3rd (Martins et al., 2013) RBG-1st RBG-3rd (Martins et al. 2013) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 13 / 18

  25. Non-projective Parsing Results (German) MST-1st, MST-2nd (McDonald et al., 2005) Turbo-1st, Turbo-3rd (Martins et al., 2013) RBG-1st RBG-3rd (Martins et al. 2013) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 13 / 18

  26. Non-projective Parsing Results (Czech) MST-1st, MST-2nd ((McDonald et al., 2005) Turbo-1st, Turbo-3rd (Martins et al., 2013) RBG-1st RBG-3rd (Martins et al. 2013) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 14 / 18

  27. Non-projective Parsing Results (Czech) MST-1st, MST-2nd ((McDonald et al., 2005) Turbo-1st, Turbo-3rd (Martins et al., 2013) RBG-1st RBG-3rd (Martins et al. 2013) Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 14 / 18

  28. Unlabeled Exact Match PTB CTB Parser Dev Test Dev Test C&M14 43.35 40.93 32.75 32.20 Dyer15 51.94 50.70 39.72 37.23 DeNSe 51.24 49.34 34.74 33.66 DeNSe +E 36.49 35.13 52.47 50.79 Table: UEM results on PTB and CTB. Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 15 / 18

  29. UAS v.s. Length 96 95 94 UAS (%) 93 92 91 C&M14 DeNSe+E 90 Dyer15 89 11 14 17 20 23 26 28 32 38 118 PTB sentence length Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 16 / 18

  30. UAS v.s. Length 93 92 91 90 89 88 UAS (%) 87 86 85 84 83 C&M14 DeNSe+E 82 Dyer15 81 80 5 9 14 18 22 26 30 37 49 116 PTB sentence length CTB CTB Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 16 / 18

  31. Conclusions We propose a dependency parser as greedily selecting the head of each word in sentence. Combine the greedy model with a MST algorithm can further increase the performance Code available: https://github.com/XingxingZhang/dense parser Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 17 / 18

  32. Thanks Q & A Zhang et al. (Univ. of Edinburgh) DeNSe : Dependency Neural Selection April 6, 2017 18 / 18

Download Presentation
Download Policy: The content available on the website is offered to you 'AS IS' for your personal information and use only. It cannot be commercialized, licensed, or distributed on other websites without prior consent from the author. To download a presentation, simply click this link. If you encounter any difficulties during the download process, it's possible that the publisher has removed the file from their server.

Recommend


More recommend