learning to recognize discontiguous entities
play

Learning to Recognize Discontiguous Entities Aldrian Obaja Muis and - PowerPoint PPT Presentation

Introduction Our Model Experiments Ambiguity Conclusion Appendix Learning to Recognize Discontiguous Entities Aldrian Obaja Muis and Wei Lu Singapore University of Technology and Design aldrian muis@sutd.edu.sg luwei@sutd.edu.sg


  1. Introduction Our Model Experiments Ambiguity Conclusion Appendix Discontiguous Entity Recognition Definition A task to recognize entities in text, where they can be discontiguous (and possibly overlapping with each other) Examples from SemEval 2014 Task 7: Analysis of Clinical Text: EGD showed hiatal hernia and vertical laceration in distal esophagus with blood in stomach and overlying lac. hiatal hernia 1 laceration . . . esophagus 2 blood in stomach 3 stomach . . . lac 4 Infarctions either water shed or embolic Infarctions 1 Infarctions . . . water shed 2 Infarctions . . . embolic 3 4 / 37

  2. Introduction Our Model Experiments Ambiguity Conclusion Appendix Previous Approaches In SemEval 2014 Task 7, there were only two teams that could handle discontiguous and overlapping entities: line1 line2 line1 line2 line1 line2 5 / 37

  3. Introduction Our Model Experiments Ambiguity Conclusion Appendix Previous Approaches In SemEval 2014 Task 7, there were only two teams that could handle discontiguous and overlapping entities: 1 Pathak et al. (2014) 5 5 Parth Pathak et al. (2014). “ezDI: A Hybrid CRF and SVM based Model for Detecting and Encoding Disorder Mentions in Clinical Notes”. In: SemEval 2014 line1 line2 line1 line2 5 / 37

  4. Introduction Our Model Experiments Ambiguity Conclusion Appendix Previous Approaches In SemEval 2014 Task 7, there were only two teams that could handle discontiguous and overlapping entities: 1 Pathak et al. (2014) 5 Standard NER using BIO tagset pipelined with SVM to combine the spans 5 Parth Pathak et al. (2014). “ezDI: A Hybrid CRF and SVM based Model for Detecting and Encoding Disorder Mentions in Clinical Notes”. In: SemEval 2014 line1 line2 line1 line2 5 / 37

  5. Introduction Our Model Experiments Ambiguity Conclusion Appendix Previous Approaches In SemEval 2014 Task 7, there were only two teams that could handle discontiguous and overlapping entities: 1 Pathak et al. (2014) 5 Standard NER using BIO tagset pipelined with SVM to combine the spans 2 Zhang et al. (2014) 6 (best team) 5 Parth Pathak et al. (2014). “ezDI: A Hybrid CRF and SVM based Model for Detecting and Encoding Disorder Mentions in Clinical Notes”. In: SemEval 2014 6 Yaoyun Zhang et al. (2014). “UTH CCB: A report for SemEval 2014 – Task 7 Analysis of Clinical Text”. In: SemEval 2014 line1 line2 5 / 37

  6. Introduction Our Model Experiments Ambiguity Conclusion Appendix Previous Approaches In SemEval 2014 Task 7, there were only two teams that could handle discontiguous and overlapping entities: 1 Pathak et al. (2014) 5 Standard NER using BIO tagset pipelined with SVM to combine the spans 2 Zhang et al. (2014) 6 (best team) Use extended BIO tagset coupled with heuristics 7 5 Parth Pathak et al. (2014). “ezDI: A Hybrid CRF and SVM based Model for Detecting and Encoding Disorder Mentions in Clinical Notes”. In: SemEval 2014 6 Yaoyun Zhang et al. (2014). “UTH CCB: A report for SemEval 2014 – Task 7 Analysis of Clinical Text”. In: SemEval 2014 7 Buzhou Tang et al. (2013). “Recognizing and Encoding Discorder Concepts in Clinical Text using Machine Learning and Vector Space”. In: ShARe/CLEF Eval. Lab 5 / 37

  7. Introduction Our Model Experiments Ambiguity Conclusion Appendix Previous Approaches In SemEval 2014 Task 7, there were only two teams that could handle discontiguous and overlapping entities: 1 Pathak et al. (2014) 5 Standard NER using BIO tagset pipelined with SVM to combine the spans 2 Zhang et al. (2014) 6 (best team) Use extended BIO tagset coupled with heuristics 7 B , I for contiguous tokens 5 Parth Pathak et al. (2014). “ezDI: A Hybrid CRF and SVM based Model for Detecting and Encoding Disorder Mentions in Clinical Notes”. In: SemEval 2014 6 Yaoyun Zhang et al. (2014). “UTH CCB: A report for SemEval 2014 – Task 7 Analysis of Clinical Text”. In: SemEval 2014 7 Buzhou Tang et al. (2013). “Recognizing and Encoding Discorder Concepts in Clinical Text using Machine Learning and Vector Space”. In: ShARe/CLEF Eval. Lab 5 / 37

  8. Introduction Our Model Experiments Ambiguity Conclusion Appendix Previous Approaches In SemEval 2014 Task 7, there were only two teams that could handle discontiguous and overlapping entities: 1 Pathak et al. (2014) 5 Standard NER using BIO tagset pipelined with SVM to combine the spans 2 Zhang et al. (2014) 6 (best team) Use extended BIO tagset coupled with heuristics 7 B , I for contiguous tokens BD , ID for discontiguous tokens 5 Parth Pathak et al. (2014). “ezDI: A Hybrid CRF and SVM based Model for Detecting and Encoding Disorder Mentions in Clinical Notes”. In: SemEval 2014 6 Yaoyun Zhang et al. (2014). “UTH CCB: A report for SemEval 2014 – Task 7 Analysis of Clinical Text”. In: SemEval 2014 7 Buzhou Tang et al. (2013). “Recognizing and Encoding Discorder Concepts in Clinical Text using Machine Learning and Vector Space”. In: ShARe/CLEF Eval. Lab 5 / 37

  9. Introduction Our Model Experiments Ambiguity Conclusion Appendix Previous Approaches In SemEval 2014 Task 7, there were only two teams that could handle discontiguous and overlapping entities: 1 Pathak et al. (2014) 5 Standard NER using BIO tagset pipelined with SVM to combine the spans 2 Zhang et al. (2014) 6 (best team) Use extended BIO tagset coupled with heuristics 7 B , I for contiguous tokens BD , ID for discontiguous tokens BH , IH for overlapping tokens 5 Parth Pathak et al. (2014). “ezDI: A Hybrid CRF and SVM based Model for Detecting and Encoding Disorder Mentions in Clinical Notes”. In: SemEval 2014 6 Yaoyun Zhang et al. (2014). “UTH CCB: A report for SemEval 2014 – Task 7 Analysis of Clinical Text”. In: SemEval 2014 7 Buzhou Tang et al. (2013). “Recognizing and Encoding Discorder Concepts in Clinical Text using Machine Learning and Vector Space”. In: ShARe/CLEF Eval. Lab 5 / 37

  10. Introduction Our Model Experiments Ambiguity Conclusion Appendix Encoding in Model of Zhang et al. Infarctions either water shed or embolic Example taken from the full sentence: “ ... protocol to evaluate for any infarctions, either water shed or embolic, ... ” 6 / 37

  11. Introduction Our Model Experiments Ambiguity Conclusion Appendix Encoding in Model of Zhang et al. [Infarctions] 1 either [water shed] 1 or embolic 1 Infarctions ... water shed Example taken from the full sentence: “ ... protocol to evaluate for any infarctions, either water shed or embolic, ... ” 6 / 37

  12. Introduction Our Model Experiments Ambiguity Conclusion Appendix Encoding in Model of Zhang et al. [[Infarctions] 1 ] 2 either [water shed] 1 or [embolic] 2 1 Infarctions ... water shed 2 Infarctions ... embolic Example taken from the full sentence: “ ... protocol to evaluate for any infarctions, either water shed or embolic, ... ” 6 / 37

  13. Introduction Our Model Experiments Ambiguity Conclusion Appendix Encoding in Model of Zhang et al. [[[Infarctions] 1 ] 2 ] 3 either [water shed] 1 or [embolic] 2 1 Infarctions ... water shed 2 Infarctions ... embolic 3 Infarctions Example taken from the full sentence: “ ... protocol to evaluate for any infarctions, either water shed or embolic, ... ” 6 / 37

  14. Introduction Our Model Experiments Ambiguity Conclusion Appendix Encoding in Model of Zhang et al. [[[Infarctions] 1 ] 2 ] 3 either [water shed] 1 or [embolic] 2 O O 1 Infarctions ... water shed 2 Infarctions ... embolic 3 Infarctions Example taken from the full sentence: “ ... protocol to evaluate for any infarctions, either water shed or embolic, ... ” 6 / 37

  15. Introduction Our Model Experiments Ambiguity Conclusion Appendix Encoding in Model of Zhang et al. [[[Infarctions] 1 ] 2 ] 3 either [water shed] 1 or [embolic] 2 BH O O 1 Infarctions ... water shed 2 Infarctions ... embolic 3 Infarctions Example taken from the full sentence: “ ... protocol to evaluate for any infarctions, either water shed or embolic, ... ” 6 / 37

  16. Introduction Our Model Experiments Ambiguity Conclusion Appendix Encoding in Model of Zhang et al. [[[Infarctions] 1 ] 2 ] 3 either [water shed] 1 or [embolic] 2 BH O BD ID O 1 Infarctions ... water shed 2 Infarctions ... embolic 3 Infarctions Example taken from the full sentence: “ ... protocol to evaluate for any infarctions, either water shed or embolic, ... ” 6 / 37

  17. Introduction Our Model Experiments Ambiguity Conclusion Appendix Encoding in Model of Zhang et al. [[[Infarctions] 1 ] 2 ] 3 either [water shed] 1 or [embolic] 2 BH O BD ID O BD 1 Infarctions ... water shed 2 Infarctions ... embolic 3 Infarctions Example taken from the full sentence: “ ... protocol to evaluate for any infarctions, either water shed or embolic, ... ” 6 / 37

  18. Introduction Our Model Experiments Ambiguity Conclusion Appendix Encoding in Model of Zhang et al. [[[Infarctions] 1 ] 2 ] 3 either [water shed] 1 or [embolic] 2 BH O BD ID O BD 1 Infarctions ... water shed 2 Infarctions ... embolic 3 Infarctions This is the canonical encoding of this particular set of entities Example taken from the full sentence: “ ... protocol to evaluate for any infarctions, either water shed or embolic, ... ” 6 / 37

  19. Introduction Our Model Experiments Ambiguity Conclusion Appendix Decoding in Model of Zhang et al. Infarctions either water shed or embolic BH O BD ID O BD 7 / 37

  20. Introduction Our Model Experiments Ambiguity Conclusion Appendix Decoding in Model of Zhang et al. Infarctions either [water shed] 1 or [embolic] 1 BH O BD ID O BD 7 / 37

  21. Introduction Our Model Experiments Ambiguity Conclusion Appendix Decoding in Model of Zhang et al. Infarctions either water shed or embolic BH O BD ID O BD 7 / 37

  22. Introduction Our Model Experiments Ambiguity Conclusion Appendix Decoding in Model of Zhang et al. [Infarctions] 1 either [water shed] 1 or embolic BH O BD ID O BD 1 Infarctions ... water shed 7 / 37

  23. Introduction Our Model Experiments Ambiguity Conclusion Appendix Decoding in Model of Zhang et al. [[Infarctions] 1 ] 2 either [water shed] 1 or [embolic] 2 BH O BD ID O BD 1 Infarctions ... water shed 2 Infarctions ... embolic 7 / 37

  24. Introduction Our Model Experiments Ambiguity Conclusion Appendix Decoding in Model of Zhang et al. [[Infarctions] 1 ] 2 either [water shed] 1 or [embolic] 2 BH O BD ID O BD 1 Infarctions ... water shed 2 Infarctions ... embolic 3 Infarctions (?) 7 / 37

  25. Introduction Our Model Experiments Ambiguity Conclusion Appendix Decoding in Model of Zhang et al. [[Infarctions] 1 ] 2 either [water shed] 1 or [embolic] 2 BH O BD ID O BD 1 Infarctions ... water shed 2 Infarctions ... embolic 3 Infarctions (?) Ambiguous! 7 / 37

  26. Introduction Our Model Experiments Ambiguity Conclusion Appendix Number of Entity Combinations In a sentence with n words, there are: 1 2 n − 1 possible discontiguous entities 8 / 37

  27. Introduction Our Model Experiments Ambiguity Conclusion Appendix Number of Entity Combinations In a sentence with n words, there are: 1 2 n − 1 possible discontiguous entities 2 2 2 n − 1 possible combinations of discontiguous entities * 8 / 37

  28. Introduction Our Model Experiments Ambiguity Conclusion Appendix Discontiguous Entities Recognition 1 How to efficiently model these discontiguous (and possibly overlapping) entities? 9 / 37

  29. Introduction Our Model Experiments Ambiguity Conclusion Appendix Discontiguous Entities Recognition 1 How to efficiently model these discontiguous (and possibly overlapping) entities? 2 How to compare the ambiguity between models for discontiguous entities? 9 / 37

  30. Introduction Our Model Experiments Ambiguity Conclusion Appendix Contributions In this paper, we contributed: 1 A new hypergraph-based model to handle discontiguous entities better 10 / 37

  31. Introduction Our Model Experiments Ambiguity Conclusion Appendix Contributions In this paper, we contributed: 1 A new hypergraph-based model to handle discontiguous entities better 2 A simple theoretical framework to compare ambiguity between models 10 / 37

  32. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model water or Infarctions either shed embolic A A A A A A E E E E E E T T T T T T X X X X X X B 0 B 0 B 0 B 0 B 0 B 0 X X X X X X O 1 O 1 O 1 O 1 O 1 O 1 B 1 B 1 B 1 B 1 B 1 B 1 X X X X X X 11 / 37

  33. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model water water or Infarctions Infarctions either shed shed embolic embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 O 1 O 1 O 1 Infarctions B 1 B 1 B 1 Infarctions . . . water shed X Infarctions . . . embolic X 12 / 37

  34. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model Key ideas: 1 Build a hypergraph that can encode any entity combination 13 / 37

  35. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model Key ideas: 1 Build a hypergraph that can encode any entity combination 2 For any sentence annotated with entities, there would be a unique subgraph that represents it (canonical encoding) 13 / 37

  36. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model Key ideas: 1 Build a hypergraph that can encode any entity combination 2 For any sentence annotated with entities, there would be a unique subgraph that represents it (canonical encoding) 3 Each entity is represented as a path in the entity-encoded hypergraph, where the B -nodes indicate which tokens are part of the entity 13 / 37

  37. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 O 1 O 1 O 1 Infarctions B 1 B 1 B 1 Infarctions . . . water shed X Infarctions . . . embolic X 14 / 37

  38. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X 14 / 37

  39. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 14 / 37

  40. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X Infarctions 14 / 37

  41. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 Infarctions 14 / 37

  42. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 Infarctions B 1 14 / 37

  43. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 Infarctions B 1 B 1 14 / 37

  44. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions Infarctions either water water shed shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 Infarctions B 1 B 1 Infarctions . . . water shed X 14 / 37

  45. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 O 1 Infarctions B 1 B 1 Infarctions . . . water shed X 14 / 37

  46. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 O 1 O 1 Infarctions B 1 B 1 Infarctions . . . water shed X 14 / 37

  47. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 O 1 O 1 O 1 Infarctions B 1 B 1 Infarctions . . . water shed X 14 / 37

  48. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions either water shed embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 O 1 O 1 O 1 Infarctions B 1 B 1 B 1 Infarctions . . . water shed X 14 / 37

  49. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model or Infarctions Infarctions either water shed embolic embolic A A A A A A E E E E E E T T T T T T X X X X X B 0 X O 1 O 1 O 1 O 1 Infarctions B 1 B 1 B 1 Infarctions . . . water shed X Infarctions . . . embolic X 14 / 37

  50. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model Training and predicting: 1 Training: Maximize conditional log-likelihood of training data 15 / 37

  51. Introduction Our Model Experiments Ambiguity Conclusion Appendix Our Hypergraph-based Model Training and predicting: 1 Training: Maximize conditional log-likelihood of training data 2 Predicting: Use Viterbi to find the highest-scoring subgraph 15 / 37

  52. Introduction Our Model Experiments Ambiguity Conclusion Appendix Experiments 16 / 37

  53. Introduction Our Model Experiments Ambiguity Conclusion Appendix Experimental Setup Dataset taken from SemEval 2014 Task 7, taking sentences containing discontiguous entities 17 / 37

  54. Introduction Our Model Experiments Ambiguity Conclusion Appendix Experimental Setup Dataset taken from SemEval 2014 Task 7, taking sentences containing discontiguous entities Two setups for training set: “Discontiguous” (smaller) and “Original” (larger) 17 / 37

  55. Introduction Our Model Experiments Ambiguity Conclusion Appendix Experimental Setup Dataset taken from SemEval 2014 Task 7, taking sentences containing discontiguous entities Two setups for training set: “Discontiguous” (smaller) and “Original” (larger) Models optimized for F1-score in dev set by varying λ 17 / 37

  56. Introduction Our Model Experiments Ambiguity Conclusion Appendix Experimental Setup Dataset taken from SemEval 2014 Task 7, taking sentences containing discontiguous entities Two setups for training set: “Discontiguous” (smaller) and “Original” (larger) Models optimized for F1-score in dev set by varying λ Features followed Tang et al. (2013): words, POS, Brown cluster, semantic category, . . . 17 / 37

  57. Introduction Our Model Experiments Ambiguity Conclusion Appendix Results Using Smaller Training Set Li-Enh Li-All Sh-Enh Sh-All 100 80 76 . 90 76 . 00 Score (%) 60 54 . 70 52 . 70 52 . 80 47 . 00 44 . 90 41 . 20 40 . 10 40 . 50 40 22 . 70 20 15 . 20 0 Precision Recall F1-score 18 / 37

  58. Introduction Our Model Experiments Ambiguity Conclusion Appendix Results Using Larger Training Set Li-Enh Li-All Sh-Enh Sh-All 100 80 73 . 90 73 . 40 64 . 10 59 . 00 59 . 10 Score (%) 60 53 . 90 52 . 80 51 . 10 49 . 40 49 . 10 49 . 50 46 . 50 40 20 0 Precision Recall F1-score 19 / 37

  59. Introduction Our Model Experiments Ambiguity Conclusion Appendix Ambiguity 20 / 37

  60. Introduction Our Model Experiments Ambiguity Conclusion Appendix Ambiguity One encoding can have multiple interpretations (set of entities) apparent [atrial [pacemaker] 2 artifact] 1 without [capture] 2 A A A A A A 1 atrial pacemaker artifact 2 E E E E E E pacemaker . . . capture T T T T T T X X X X B 0 B 0 B 0 1 pacemaker artifact atrial pacemaker artifact 2 atrial pacemaker . . . capture X pacemaker artifact O 1 O 1 B 1 pacemaker . . . capture X atrial pacemaker . . . capture 1 infarctions . . . water shed 2 infarctions . . . embolic Infarctions either water shed or embolic BH O BD ID O BD 1 infarctions 2 infarctions . . . water shed 3 infarctions . . . embolic 21 / 37

  61. Introduction Our Model Experiments Ambiguity Conclusion Appendix Ambiguity The models need further processing after prediction to generate one set of entities 22 / 37

  62. Introduction Our Model Experiments Ambiguity Conclusion Appendix Ambiguity The models need further processing after prediction to generate one set of entities We compare two heuristics: 22 / 37

  63. Introduction Our Model Experiments Ambiguity Conclusion Appendix Ambiguity The models need further processing after prediction to generate one set of entities We compare two heuristics: All : Return the union of all possible interpretations 1 22 / 37

  64. Introduction Our Model Experiments Ambiguity Conclusion Appendix Ambiguity The models need further processing after prediction to generate one set of entities We compare two heuristics: All : Return the union of all possible interpretations 1 Enough : Return one possible interpretation 2 22 / 37

  65. Introduction Our Model Experiments Ambiguity Conclusion Appendix Ambiguity 23 / 37

  66. Introduction Our Model Experiments Ambiguity Conclusion Appendix Ambiguity Definition Ambiguity level A ( M ) of model M is the average number of interpretations of each canonical encoding in the model 23 / 37

  67. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? 24 / 37

  68. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline model: 24 / 37

  69. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline model: There are 7 possible tags per word (B, I, BD, ID, BH, IH, O) 24 / 37

  70. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline model: There are 7 possible tags per word (B, I, BD, ID, BH, IH, O) The model can output any combination of those: 7 n 24 / 37

  71. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline model: There are 7 possible tags per word (B, I, BD, ID, BH, IH, O) The model can output any combination of those: 7 n Not all are canonical, so: M Li ( n ) < 7 n < 2 3 n 24 / 37

  72. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline model: There are 7 possible tags per word (B, I, BD, ID, BH, IH, O) The model can output any combination of those: 7 n Not all are canonical, so: M Li ( n ) < 7 n < 2 3 n For our hypergraph-based model: 24 / 37

  73. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline model: There are 7 possible tags per word (B, I, BD, ID, BH, IH, O) The model can output any combination of those: 7 n Not all are canonical, so: M Li ( n ) < 7 n < 2 3 n For our hypergraph-based model: Number of canonical encoding = number of subgraphs 24 / 37

  74. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline model: There are 7 possible tags per word (B, I, BD, ID, BH, IH, O) The model can output any combination of those: 7 n Not all are canonical, so: M Li ( n ) < 7 n < 2 3 n For our hypergraph-based model: Number of canonical encoding = number of subgraphs Q : How to calculate the number of subgraphs? 24 / 37

  75. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings A : Use dynamic programming on combination of nodes 25 / 37

  76. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings A : Use dynamic programming on combination of nodes Fig. 1: Simplified graph to illustrate subgraph counting 25 / 37

  77. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings A : Use dynamic programming on combination of nodes Fig. 1: Simplified graph to illustrate Fig. 2: State transitions subgraph counting 25 / 37

  78. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings A : Use dynamic programming on combination of nodes Fig. 1: Simplified graph to illustrate Fig. 2: State transitions subgraph counting f 11 ( n ) = 2 ∗ f 11 ( n − 1) + f 01 ( n − 1) (1) 25 / 37

  79. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline: There are 7 possible tags per word (B, I, BD, ID, BH, IH, O) The model can output any combination of those: 7 n Not all are canonical, so: M Li ( n ) < 7 n < 2 3 n For our hypergraph-based model: Number of canonical encoding = number of subgraphs 26 / 37

  80. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline: There are 7 possible tags per word (B, I, BD, ID, BH, IH, O) The model can output any combination of those: 7 n Not all are canonical, so: M Li ( n ) < 7 n < 2 3 n For our hypergraph-based model: Number of canonical encoding = number of subgraphs After more calculations: M Sh ( n ) > C · 2 10 n 26 / 37

  81. Introduction Our Model Experiments Ambiguity Conclusion Appendix Counting Number of Encodings How many canonical encodings do the models have? For the baseline: There are 7 possible tags per word (B, I, BD, ID, BH, IH, O) The model can output any combination of those: 7 n Not all are canonical, so: M Li ( n ) < 7 n < 2 3 n For our hypergraph-based model: Number of canonical encoding = number of subgraphs After more calculations: M Sh ( n ) > C · 2 10 n So our model is less ambiguous compared to the baseline model 26 / 37

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