Transcript 771Lec19-WordMeaningsII

CSCE 771
Natural Language Processing
Lecture 19
Word Meanings II
Topics
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Description Logic III
Overview of Meaning
Readings:
 Text Chapter 189NLTK book Chapter 10
March 27, 2013
Overview
Last Time (Programming)
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Wordnet overview
Today
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Computational Semantics
Feature based grammars
Readings:
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Text 19
NLTK Book: Chapters 9 and 10
Next Time: Computational Lexical Semantics
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HW review
Dropboxes
1.
2.
3.
4.
frequency distribution - Handbook Assignment
Regular Expression /urllib2 - Identify prerequisites Assignment
Extend backoff tagger to include trigram Assignment
Test1
Soon to exist:
NER for handbook
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Wordnet
Most synsets are connected to other synsets via a number of
semantic relations. These relations vary based on the type of
word, and include:
Nouns
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hypernyms: Y is a hypernym of X if every X is a (kind of) Y (canine
is a hypernym of dog) “superordinate” “superclass”
hyponyms: Y is a hyponym of X if every Y is a (kind of) X (dog is a
hyponym of canine) “IS-A”
coordinate terms: Y is a coordinate term of X if X and Y share a
hypernym (wolf is a coordinate term of dog, and dog is a coordinate
term of wolf) “sibling”
holonym: Y is a holonym of X if X is a part of Y (building is a
holonym of window) “HAS-PART”
meronym: Y is a meronym of X if Y is a part of X (window is a
meronym of building) “IS-PART” “IS-MEMBER”
http://en.wikipedia.org/wiki/WordNet
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Verbs
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hypernym: the verb Y is a hypernym of the verb X if the activity X is
a (kind of) Y (to perceive is an hypernym of to listen)
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troponym: the verb Y is a troponym of the verb X if the activity Y is
doing X in some manner (to lisp is a troponym of to talk)
entailment: the verb Y is entailed by X if by doing X you must be
doing Y (to sleep is entailed by to snore)
coordinate terms: those verbs sharing a common hypernym (to lisp
and to yell)
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Adjectives
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related nouns
similar to
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participle of verb
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Adverbs
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root adjectives
http://en.wikipedia.org/wiki/WordNet
CSCE 771 Spring 2013
http://wordnet.princeton.edu/
x
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Wordnet
online
Fig 19-1
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Word senses
A word sense is a distinct meaning
Synonym sets are relations among word senses
• couch/sofa, car/automobile
antonyms also
• long/short, big/large, rise/fall
• extremes; or opposite in direction
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Fig 19-2 Noun relations in wordnet
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Fig 19-3 Verb relations in wordnet
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Fig19-4-like IS-A (hyponym) Chain for
lemma bass#7
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Sister terms (= coordinate terms)
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Thematic Roles
19.19 “Sasha broke the window.”
exists e,x,y breaking(e) & breaker(e, Sasha) &
brokenThing(e, y) & window(y)
19.20 Pat opened the door.
Deep or thematic roles
• Panini (Indian grammarian) circa 7th-4th century BC
• Fillmore 1968, Gruber 1965
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Fig 19.5 Common Thematic Roles
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19.6 Examples of Thematic Roles
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Variations of expression
• John broke the window.
• John broke the window with a rock.
• The rock broke the window.
• The window broke.
• The window was broken by John.
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Case Frames for verbs
Break
• Agent: Subject, Theme:Object
• Agent: Subject, Theme:Object, Instrument: PP-with
• Instrument:Subject, Theme:Object
• Theme: Subject
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19.4.3 Problems with Thematic Roles
Example 19.27
a. the cook opened the jar with the new gadget.
b. the new gadget opened the jar.
Example 19.28
a. Shelly ate the banana with a fork.
b. *The fork ate the banana.
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Prop Bank
PropBank is a corpus that is annotated with verbal
propositions and their arguments—a "proposition
bank".
• http://verbs.colorado.edu/~mpalmer/projects/ace.html
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http://en.wikipedia.org/wiki/PropBank
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PropBank Online
http://verbs.colorado.edu/~mpalmer/projects/ace.html
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FrameNet
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Framenet Core Roles
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FrameNet
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Selectional restrictions of roles
from PropBank
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Fig 19-7 Hamburger Edible?
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Figure 19.8 Shank’s Conceptual
Dependencies
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