Natural Language Processing

DIT410/TIN174, Artificial Intelligence

John J. Camilleri

4 April, 2017

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Room name: HORSEY


Source: http://www.denizyuret.com/2010/12/research-focus.html

Natural language

Formal language

Natural language Understanding


http://i.huffpost.com/gen/1403845/images/o-SPIKE-JONZE-HER-facebook.jpg

Natural language Processing

Information extraction

Named entity recognition


http://www.europeana-newspapers.eu/named-entity-recognition-for-digitised-newspapers/

Classification

Sentiment analysis


https://www.csc.ncsu.edu/faculty/healey/tweet_viz/

Information retrieval

Search

Machine translation

Approaches

Rule-based

Statistical

Deep learning

Phrase-structure grammars

β€œthe man saw a mountain”

↓

Context-free grammar (CFG)

terminals, non-terminals, rules

  • S β†’ NP VP
  • NP β†’ Det N
  • VP β†’ V NP
  • N β†’ man | mountain
  • V β†’ saw
  • Det β†’ a | the

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http://www.triblocal.com/highland-park-highwood/files/2012/03/stock-photo-17181584-mountain-man.jpg

Ambiguity

extending the grammar with prepositions

Parsing

input string β†’ parse tree(s)

CYK algorithm

Probabilistic parsing

Overgeneration

β€œAll grammars leak”

Solutions to overgeneration

  • In CFG
  • Other formalisms

Generative capacity

Chomsky hierarchy

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Levels of ambiguity

Lexical
Syntactic
Semantic

Models for disambiguation

Acoustic model
Language model
Mental model
World model

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Colourless green ideas sleep furiously
http://wmjasco.blogspot.se/2008/11/colorless-green-ideas-do-not-sleep.html

That’s all for today

Friday:

Semantics, Interpretation, NLP in Shrdlite

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