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CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
CSTalks-Natural Language Processing-17Aug
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CSTalks-Natural Language Processing-17Aug

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  • 1. Natural Language Processing Daniel DahlmeierNUS Graduate School for Integrative Sciences and Engineering danielhe@comp.nus.edu.sg CSTalks 2 November 2011
  • 2. Acknowledgments Examples and figures from Michael Collins’ lecture notes: http://www.cs.columbia.edu/∼mcollins. Some other figures are from Wikipedia: http://www.wikipedia.org. The rest I randomly found on the web.
  • 3. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionGoogle translate 3/25
  • 4. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionIBM’s Watson computer wins at Jeopardy! 4/25
  • 5. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionSiri 5/25
  • 6. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionWhat is Natural Language Processing? Natural Language Processing (NLP) or Computational Linguistics Language processing that goes beyond a “bag of words” representation. Example Translate from one language into the other. Answer natural language questions. Parse the syntactic/semantic structure of a sentence. The other NLP NLP = neuro-linguistic programming. 6/25
  • 7. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionBackground(s): Artificial Intelligence Talk to your computer Dave: Hello, HAL. Do you read me, HAL? HAL: Affirmative, Dave. I read you. Dave: Open the pod bay doors, HAL. HAL: I’m sorry, Dave. I’m afraid I can’t do that. The computer needs to ... Understand the user : Natural Language Understanding. Generate a well-formed reply : Natural Language Generation. 7/25
  • 8. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionBackground(s): Artificial Intelligence (cont.) Turing Test Experimenter talks to two parties A and B via a terminal. If C cannot distinguish which party is a computer and which is a human, we should consider the computer to be intelligent. Natural language is deeply intertwined with intelligence. 8/25
  • 9. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionBackground(s): Linguistics Generative Linguistics Humans can produce and understand an infinite number of sentences by means of a finite set of rules. Language is produced through a generative, recursive process in the human brain. The principles that underlie this process are universal to all languages (universal grammar). 9/25
  • 10. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionBackground(s): the Web “We are drowning in information but starved for knowledge.” by Edward Osborne Wilson Too much text to read... Wikipedia: over 3.7 million articles (English). PubMed: over 20 million citations. WWW: billions of pages, trillions of words. 10/25
  • 11. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionPart-of-speech Tagging Part-of-speech tagging Input: a sentence. Output: a part-of-speech tag sequence, e.g., noun, verb, adjective,... Example Profits/N soared/V at/P Boeing/N Co./N ,/, easily/ADV topping/V forecasts/N on/P Wall/N Street/N ./. 11/25
  • 12. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionNamed-entity recognition Named-entity recognition Input: a sentence. Output: a BIO-named entity tag sequence, e.g., PERSON, ORGANIZATION, OTHER. Example Profits/O soared/O at/O Boeing/B-ORG Co./I-ORG ,/O easily/O topping/O forecasts/O on/O Wall/O Street/O ./O 12/25
  • 13. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionWord Sense Disambiguation Word sense disambiguation Input: a sentence. Output: the sense of each word in the sentence. Example I/sense1 can/sense1 can/sense2 a/sense1 can sense3 . 13/25
  • 14. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionParsing Parsing Input: a sentence. Output: the syntactic tree structure of the sentence. Example Boeing is located in Seattle. 14/25
  • 15. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionMachine translation Machine Translation Input: a sentence in language F . Output: the translated sentence in language E . Example Input: Syriens Pr¨sident Baschar al-Assad hat den Westen davor a gewarnt, sich in die Angelegenheiten seines Landes einzumischen. Output: Syrian President Bashar al-Assad has warned the West against interfering in the affairs of his country. 15/25
  • 16. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionWhy is it hard? ( example from L.Lee) “At last, a computer that understands you like your mother” 16/25
  • 17. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionAmbiguity of Natural Language “At last, a computer that understands you like your mother” This could mean... 1 It understands you as well as your mother understands you. 2 It understands (that) you like your mother. 3 It understands you as well as it understands your mother. 1 and 3: Does this mean well, or poorly? 17/25
  • 18. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionAmbiguity at the Acoustic Level “At last, a computer that understands you like your mother” This sounds like... 1 “... a computer that understands you like your mother.” 2 “... a computer that understands you lie cured mother.” 18/25
  • 19. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionAmbiguity at the Syntactic (structure) Level “At last, a computer that understands you like your mother” 19/25
  • 20. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionAmbiguity at the Syntactic (structure) Level “List all flights on Tuesday.” 20/25
  • 21. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionAmbiguity at the Semantic (meaning) Level Definition of “mother” 1 a woman who has given birth to a child 2 a stringy slimy substance consisting of yeast cells and bacteria; is added to cider or wine to produce vinegar. More ambiguity They put money in the bank (= buried in mud?). I saw her duck with a telescope (= a duck carrying a telescope?). 21/25
  • 22. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionAmbiguity at the Discourse (multi-clause) Level Anaphora resolution Alice says they’ve built a computer that understands you like your mother. But she ... ... doesn’t know any details (Alice) ... doesn’t understand me at all (my mother) 22/25
  • 23. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionRelated Stuff Machine Learning This really made large-scale, open domain NLP applications possible. Information Retrieval Both need to “understand” language. Linguistics Interested in the nature of language. Psychology / Cognitive Science Both interested in human cognitive capabilities. 23/25
  • 24. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionConclusion What I have told you... What NLP is about. Some NLP tasks that people work on. Why it’s not that easy. What I haven’t told you How do you solve all these problems? How well does it work? What is left to be done? 24/25
  • 25. Examples What is NLP? Background NLP tasks Why is it hard? Related Stuff ConclusionWould you like to know more? NLP courses at NUS CS4248: natural language processing CS6207: advanced natural language processing Books Jurafsky and Martin, Speech and Language Processing (2nd Edition) 25/25

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