Lecture 19 Word Meanings II CSCE 771 Natural Language Processing Lecture 19 Word Meanings II Topics Description Logic III Overview of Meaning Readings: Text Chapter 189NLTK book Chapter 10 March 27, 2013

Overview Readings: Text 19 NLTK Book: Chapters 9 and 10 Last Time (Programming) Wordnet overview Today Computational Semantics Feature based grammars Readings: Text 19 NLTK Book: Chapters 9 and 10 Next Time: Computational Lexical Semantics

HW review Dropboxes Soon to exist: NER for handbook frequency distribution - Handbook Assignment Regular Expression /urllib2 - Identify prerequisites Assignment Extend backoff tagger to include trigram Assignment Test1

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 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

Verbs Adjectives Adverbs 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) 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) Adjectives related nouns similar to participle of verb Adverbs root adjectives http://en.wikipedia.org/wiki/WordNet

http://wordnet.princeton.edu/ x

Wordnet online Fig 19-1

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

Fig 19-2 Noun relations in wordnet

Fig 19-3 Verb relations in wordnet

Fig19-4-like IS-A (hyponym) Chain for lemma bass#7

Sister terms (= coordinate terms)

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

Fig 19.5 Common Thematic Roles

19.6 Examples of Thematic Roles

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.

Case Frames for verbs Break Agent: Subject, Theme:Object Agent: Subject, Theme:Object, Instrument: PP-with Instrument:Subject, Theme:Object Theme: Subject

19.4.3 Problems with Thematic Roles Example 19.27 the cook opened the jar with the new gadget. the new gadget opened the jar. Example 19.28 Shelly ate the banana with a fork. *The fork ate the banana.

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 http://en.wikipedia.org/wiki/PropBank

PropBank Online http://verbs.colorado.edu/~mpalmer/projects/ace.html

FrameNet

Framenet Core Roles

FrameNet

Selectional restrictions of roles from PropBank

Fig 19-7 Hamburger Edible?

Figure 19.8 Shank’s Conceptual Dependencies