Yliopiston etusivulle In English
Helsingin yliopisto
CLT231: Introduction to Natural Language Processing - 2010-2011

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12. WordNet and Word Senses.

  • Lecture notes
  • Further reading
  • Practical work
    • In IDLE do:
      >>> import nltk
      >>> from nltk.corpus import wordnet as wn
      
    • List the synonym sets of dog and count them:
      >>> wn.synsets('dog')
      >>> len(wn.synsets('dog'))
      
    • Do the same for hypernyms and hyponyms at different levels:
      >>> dog_levels = ['mammal', 'animal', 'dog', 'collie']
      >>> for word in dog_levels:
              print wn.synsets(word)
              print "Number of senses:", len(wn.synsets(word))
      
    • The polysemy of a word is the number of different senses it has. Define a function that returns the number of senses:
      >>> def polysemy(word):
              return len(wn.synsets(word))
      
    • Use the function to compare polysemy at different levels:
      >>> for word in dog_levels:
              print word, polysemy(word)
      
    • Do the same for different levels for some other words:
      >>> horse_levels = ['mammal', 'animal', 'horse', 'stallion']
      >>> for word in horse_levels:
              print word, polysemy(word)
      >>> pig_levels = ['mammal', 'animal', 'pig', 'sow']
      >>> for word in pig_levels:
              print word, polysemy(word)
      
    • This suggests that basic categories like dog, horse, pig have more senses than higher and lower levels. Do you agree?
    • It's clearer if only noun senses are counted (sow is also a verb). Define a new function that counts only the noun senses:
      >>> def noun_polysemy(word):
              return len(wn.synsets(word, pos='n'))
      >>> for word in pig_levels:
              print word, noun_polysemy(word)
      

Assignment 4.

© 2006-2010 Graham Wilcock

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