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ULM-1 Understanding Languages by Machines: The borders of Ambiguity

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In this presentation will explore the closed world of language as a system of word relations. Words and texts are highly ambiguous, but we believe the complete
scope and complexity of this ambiguity is not well defined yet. The goal is to more properly define the problem and find the optimal solution given the vast volumes of textual data that are available.
Most of the WSD systems are not tacking properly the problem and the context is not being modelled in a proper way. Besides to this, lately WSD has been changed from a purely lexical approach
(static view) to a reference approach (dynamic view). Considering these two facts, the role of the background and discourse information is crucial.
To prove our hypothesis about what WSD systems are not facing properly, we performed an error analysis on the participant outputs of the SensEval/SemEval WSD competitions. Interesting and
surprising conclusions came out of this analysis.
Finally, our participation on the last SemEval-2015 task 13: Multilingual All-Words WSD and Entity Linking. In our system we implement our ideas about using background information to perform WSD.

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ULM-1 Understanding Languages by Machines: The borders of Ambiguity

  1. 1. ULM-1 Understanding Language by Machines The Borders of Ambiguity Ruben Izquierdo ruben.izquierdobevia@vu.nl http://rubenizquierdobevia.com
  2. 2. Structure  Part I  The ULM-1 project  Part II  Error analysis on WSD  Part III  Using Background Information to Perform WSD  Part IV  What is next? Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 2
  3. 3. Who am I?  Ruben Izquierdo Bevia  Computer Science, Alicante, Spain 2004  2004-2011 researcher at the University of Alicante  September 2010, Alicante  Phd. Thesis: An approach to Word Sense Disambiguation based on Supervised Machine Learning and Semantic Classes  Sept 2011  Sept 2012  DutchSemCor project (Tilburg and VU universities, NL)  Sept 2012  Sept 2014  Opener project (VU University, NL)  Sept 2014   ULM1 Spinoza project Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 3
  4. 4. Part I Understanding Language by Machines Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 4
  5. 5. Understanding Languages by Machines  NWO (Netherlands Organization for Scientific Research)  Spinoza Price  Highest Dutch award in science for top researchers with international reputation  Piek Vossen was one of the three winners in 2013  Some money for research  4 ULM projects Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 5
  6. 6. Understanding Languages by Machines  Develop computer models that assign deeper meaning to language and approximates human understanding  Use the models to automatically read and understand texts  Words and texts are highly ambiguous  Get a better understanding of the scope and complexity of this ambiguity Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 6
  7. 7. Understanding Languages by Machines  ULM-1: The borders of ambiguity  Word relations and ambiguity  Define the problem and find an optimal solution  ULM-2: Word, Concept, Perception and Brain  Relate words and meanings to perceptual data and brain activation patterns  ULM-3: From timelines to storylines  Interpretation of words and our way of interacting with the changing world  Structure these changes as stories along explanatory motivations  ULM-4: A quantum model of text understanding  Technical model  Move from pipeline approaches which take early decisions to a model there the final interpretation is carried out by high-order semantic and contextual models Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 7
  8. 8. Understanding Languages by Machines  ULM-1: The borders of ambiguity  Word relations and ambiguity  Define the problem and find an optimal solution  ULM-2: Word, Concept, Perception and Brain  Relate words and meanings to perceptual data and brain activation patterns  ULM-3: From timelines to storylines  Interpretation of words and our way of interacting with the changing world  Structure these changes as stories along explanatory motivations  ULM-4: A quantum model of text understanding  Technical model  Move from pipeline approaches which take early decisions to a model there the final interpretation is carried out by high-order semantic and contextual models Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 8
  9. 9. ULM-1: The Borders of Ambiguity Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 9 Piek Vossen Marten Postma Ruben Izquierdo
  10. 10. Word Sense Disambiguation WSD  “The problem of computationally determining which ‘sense’ of a word is activated by the use of that word in a particular context” (Agirre & Edmonds, 2006) Our1 project14 looks14 into1 breaking60 the1 borders10 of1 ambiguity1, for1 which1 the1 queen12 piece18 is13 an1 example1 1.981.324.800 interpretations !!! Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 10
  11. 11. Classical Approaches  Supervised approaches  Require annotated data  Problems with domain adaptation  Knowledge based  Dependent on the resources  Unsupervised approaches  Low performance  Require large amount of data Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 11
  12. 12. Still Unsolved WSD is still considered to be “unsolved” Competition Year Type Baseline Best F1 SensEval2 2001 all-words 57.0 69.0 (Sup) SensEval3 2004 All-words 60.9 65.1 (Sup) SemEval1 2007 All-words (task 17) 51.4 59.1 (Sup) SemEval2 2010 All-words on specific domain 50.5 56.2 (Kb) Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 12
  13. 13. General Trends  Look at WSD as a purely classification problem  Focus more on the low level algorithm than on the WSD problem itself  Poor representation of the context  Following the idea: “the more features, the better performance”  Usually Bag-of-words features Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 13
  14. 14. … but … what about the discourse and background information? Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 14
  15. 15. Discourse and Background Knowledge The winner will walk away with $1.5 million source: http://www.southafrica.info/news/sport/golf- nedbank- 210613.htm#.VEAWkYusVW8 Creation time: 21 June 2013 Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 15
  16. 16. Discourse and Background Knowledge The winner will walk away with $1.5 million source: http://www.southafrica.info/news/sport/golf- nedbank- 210613.htm#.VEAWkYusVW8 Creation time: 21 June 2013 Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 16 Winner  the contestant who wins the contest (wordnet synset ENG30-10782940-n)
  17. 17. Discourse and Background Knowledge The winner will walk away with $1.5 million source: http://www.southafrica.info/news/sport/golf- nedbank- 210613.htm#.VEAWkYusVW8 Creation time: 21 June 2013 Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 17 The winner won the Nedbank Golf Challengue
  18. 18. Discourse and Background Knowledge The winner will walk away with $1.5 million source: http://www.southafrica.info/news/sport/golf- nedbank- 210613.htm#.VEAWkYusVW8 Creation time: 21 June 2013 Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 18 The winner was  Thomas Bjørn
  19. 19. Borders of Ambiguity Lexical WSD: WordNet sense of winner Discourse information: “winner” is the winner of the Nedbank Golf Challenge Referential WSD: the “winner” is Thomas Børjn WordNet Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 19
  20. 20. The Role of Background knowledge “One of the best moves by Gary Kasparov which includes a queen sacrifice…” Source: http://www.chess.com/forum/view/chess-players/kasparov-queen-sacrifice Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 20
  21. 21. The Role of Background knowledge “One of the best moves by Gary Kasparov which includes a queen sacrifice…” Source: http://www.chess.com/forum/view/chess-players/kasparov-queen-sacrifice STATE OF THE ART SYSTEM It-makes-sense WSD system (Zhong and Ng, 2010) • 36% queen.n.1: the only fertile female in a colony of social insects such as bees, ants or termites. • 34% queen.n.2: a female sovereign ruler • 30% queen.n.3: the wife or widow of a king • ….. • 0% queen.n.6: the most powerful chess piece Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 21
  22. 22. The Role of Background knowledge  A very naïve approach  Find “Gary Kasparov” as an entity and link it to Wikipedia  Compare textual overlapping of:  Wikipage Queen_chess  Wikipage Gary_Kasparov  170 overlapping types  Wikipage Queen_regnant  Wikipage Gary_Kasparov  88 overlapping types Examples of matching words Queen_chess – G. Kasparov board opening matches game press championship rules chess player king queen Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 22
  23. 23. Our ideal system Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 23
  24. 24. Part II Error Analysis of WSD systems Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 24 Piek Vossen Marten Postma Ruben Izquierdo
  25. 25. Motivation Word Sense Disambiguation is still an unsolved problem Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 25
  26. 26. Hypothesis  Little attention has been paid to the problem  WSD as just 1 problem  The context is not being exploited properly  Systems rely too much on the Most Frequent Sense  It is indeed the baseline, very hard to overcome Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 26
  27. 27. Goal of the Analysis  Perform error analysis of the participant systems on previous WSD evaluations to prove our hypothesis  Senseval-2: all-words task  Senseval-3: all-words task  Semeval2007: all-words task (#17)  Semeval2010: all-words on specific domain (#17)  Semeval2013: multilingual all-words WSD and entity linking (#12) Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 27
  28. 28. Analysis  Calculate the performance of the systems according to different criteria of the gold data  Monosemous / polysemous  Part-of-speech  Most Frequent Sense vs. Non MFS  Polysemy class  Frequency class Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 28
  29. 29. Monosemous errors Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 29
  30. 30. Monosemous Errors Competition Monosemou s Wrong Examples Senseval2 499 (20.9%) 37.5% gene.n (suppressor_gene.n), chance.a (chance.n) next.r (next.a) Senseval3 334 (16.6%) 44.1% Datum.n (data.n) making.n (make.v) out_of_sight (sight) Semeval2007 25 (5.5%) 11.1% get_stuck.v, lack.v, write_about.v Semeval2010 31 (2.2%) 97.9% Tidal_zone.n pine_marten.n roe_deer.n cordgrass.n Semeval2013 (lemmas) 348 (21.1%) 1.9% Private_enterprise, developing_country, narrow_margin Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 30
  31. 31. Most Frequent Sense Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 31
  32. 32. Most Frequent Sense  When the correct sense is NOT the most frequent sense  Systems still assign mostly the MFS  Senseval2  799 tokens are not MFS  84% systems still assign the MFS  Most “failed” words due to MFS bias  Senseval2, senseval3  Say.v find.v take.v have.v cell.n church.n  Semeval2010  Area.n nature.n connection.n water.n population.n Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 32
  33. 33. Analysis per PoS-tag Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 33
  34. 34. Polysemy Profile Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 34
  35. 35. Frequency Class Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 35
  36. 36. Expected vs. Observed difficulty  Calculate per sentence  The “expected” difficulty  Average polysemy, sentence length, average word length Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 36
  37. 37. Expected vs. Observed difficulty  Calculate per sentence  The “expected” difficulty  Average polysemy, sentence length, average word length Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 37
  38. 38. Expected vs. Observed difficulty  Calculate per sentence  The “expected” difficulty  Average polysemy, sentence length, average wor length  The “observed” difficulty  From the real participant outputs, average error rate  We could expect: harder sentences higher error rate easier sentences lower error rate Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 38
  39. 39. Expected vs. Observed difficulty Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 39
  40. 40. Expected vs. Observed difficulty Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 40
  41. 41. Expected vs. Observed difficulty • The context is not (probably) exploited properly • Expected “easy” sentences SHOULD show low error rates • Occurrences of the same word in different contexts have similar error rate • The difficulty of a word depends more on its polysemy than on the context where it appears Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 41
  42. 42. WSD Corpora http://github.com/rubenIzquierdo/wsd_corpora Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 42
  43. 43. WSD Corpora Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 43
  44. 44. System Outputs https://github.com/rubenIzquierdo/sval_systems Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 44
  45. 45. System Outputs Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 45
  46. 46. Part III When to Use Background Information to Perform WSD Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 46 Piek Vossen Marten Postma Ruben Izquierdo
  47. 47. SemEval-2015 Task #13  Multilingual All-Words Sense Disambiguation and Entity Linking Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 47
  48. 48. SemEval-2015 Task #13 Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 48
  49. 49. Motivation  From the previous error analysis  MFS bias is a big problem  For both supervised and unsupervised approaches  Specially when there is domain shift  Our approach 1. Determine the predominant sense for every lemma in the specific domain (unsupervised) 2. Apply a state-of-the-art WSD system 3. Define an heuristic to determine when to apply 1) or 2) 4. We focused on WSD in English only Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 49
  50. 50. Architecture  IMS route: favors the MFS in general domain and local features  Background route: favors the predominant sense in the domain Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 50 ROUTE 1 ROUTE 2
  51. 51. Architecture Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 51
  52. 52. Architecture  Two different approaches  Online approach  The SemEval test documents (4 documents)  Offline approach  Precompiled documents for the target domain  Documents from biomedical domain  Converted to NAF  Tokens, Lemmas and PoS tags Seed documents SD Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 52
  53. 53. Architecture Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 53
  54. 54. Architecture  DBpedia spotlight is applied to the seed documents  Entities and links to DBpedia are extracted  Wikipedia pages from DBpedia links  Filter:  Consider only DBpedia links with a ontological type which is a leaf on the ontology  Better results without filter  All the wikipedia pages compile the EAC corpus Entity Article Corpus EAC Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 54
  55. 55. Architecture Entity Article Corpus EAC Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 55
  56. 56. Architecture Entity Article Corpus EAC Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 56
  57. 57. Architecture Entity Article Corpus EAC Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 57
  58. 58. Architecture Entity Article Corpus EAC Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 58
  59. 59. Architecture Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 59
  60. 60. Architecture  Targets high recall and low precision/quality  Entity Article Corpus EAC  LDA  Domain Model DM  For every document DEAC in EAC  Obtain the DBpedia type T  Obtain the set of DBpedia entities S from DBpedia which belong to T  For every document DS in S:  Compute the similarity of DS against the model DM  If similarity >= THRESHOLD  select document for the Entity expanded corpus LDA Expansion Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 60
  61. 61. Architecture LDA Expansion Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 61
  62. 62. Architecture LDA Expansion Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 62
  63. 63. Architecture LDA Expansion http://dbpedia.org/ontology/HumanGene Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 63
  64. 64. Architecture LDA Expansion Domain Model LDA Similarity Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 64 Entity Article Corpus EAC
  65. 65. Architecture Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 65
  66. 66. Architecture Entity Overlapping Expansion  Targets high quality and medium recall  Entity Article Corpus EAC  Extract all the set of entities: SE  For every entity E in SE:  Obtain all the wikilinks in E: W  For every Ew in W  Obtain all the wikilinks Wew in Ew  SW  Compute the overlap SE and SW  Filter by threshold Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 66
  67. 67. Architecture Entity Overlapping Expansion … … http://dbpedia.org/resource/CCDC11 … … SE WikiPage for CCDC11 Get wikilinks for CCDC11 … … Phosphorylation … … WikiPage for Phosphorylation Get wikilinks for Phosphorylation Phosphate Enzymes Biochemistry Prokaryotic CCDC11 wikilinks Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 67
  68. 68. Architecture Entity Overlapping Expansion … … http://dbpedia.org/resource/CCDC11 … … SE Phosphate Enzymes Biochemistry Prokaryotic Calculate overlap > THRESHOLD Select / Reject Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 68
  69. 69. Architecture Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 69
  70. 70. Architecture Predominant Sense Algorithm  Background corpus BC: EAC + EE  For every lemma L in BC:  Extract all sentences containing L  If there are more than 100 sentences  Word sense induction with Hierarchical Dirichlet Processes (Lau et al., 2012)  Induce senses using Topic Modeling  Output: list of senses with confidences per lemma Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 70
  71. 71. Architecture Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 71
  72. 72. Architecture Voting  For a new instance for a given lemma  Obtain sense ranking of Predominant Sense (PS)  Only if first 2 senses agglomerate 85% of confidence (avoid skewedness)  Mix both sense rankings  PS and ItMakesSense  Select the sense with highest confidence  If there is no Predominant Sense information  Use ItMakesSense best sense Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 72
  73. 73. Results All domains Measure All N V Precision 67.5 (2) 64.7 56.6 Recall 51.4 (5) 42.9 53.9 F1 58.4 (4) 51.6 55.2 Social Issues domain Measure All N V F1 61.2 (2) 54.8 (7) 70.6 (1) Math Computer domain Measure All N V F1 47.7 (5) 30.5 (13) 49.7 (7) Biomedical domain Measure All N V F1 66.4 (4) 62.7 (9) 53.8 (2) Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 73
  74. 74. Discussion  The domain was not just biomedical, but mixed  We couldn’t use offline approach  Online approach: small size of seed documents  We used WN1.7.1 while gold was WN3.0  Some test instances were not annotated  Only the predominant sense output  Precision nouns improved 64.7%  69.1%  Precision verbs improved 56.6%  64.6%  … but…  Recall nouns 42.9%  20.1%  Recall verbs 53.9%  17.7% Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 74
  75. 75. GitHub Code https://github.com/cltl/vua-wsd-sem2015 Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 75
  76. 76. Part IV What is next? Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 76
  77. 77. Current and Future  Most Frequent Sense Classifier  Decide when MFS apply or not  Based on the output of 2 WSD systems  UKB  IMS  Random Forest algorithm  Features  Confidence of the MFS by systems  Sense ranking entropy  WordNet Domains / SuperSense for the MFS  …  Voting for selecting the MFS Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 77
  78. 78. Current and Future  Unsupervised learning for MFS / LFS  Distributional semantics and word2vec for detecting the MFS  Vectors for representing MFS cases  Vectors for representing LFS cases  Operate with vectors  V(‘Paris’) – V(‘France’) + V(‘Italy’) => V(‘Rome’)  V(‘king’) – V(‘man’) + V(‘woman’)  V(‘queen’) Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 78
  79. 79. ULM-1 Understanding Language by Machines The Borders of Ambiguity THANKS Ruben Izquierdo ruben.izquierdobevia@vu.nl http://rubenizquierdobevia.com
  80. 80. SemEval2013 datasets Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 80
  81. 81. SemEval2013 results Ruben Izquierdo, Nov 2015 “The Borders of Ambiguity” 81

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