124.11.lec11

124.11.lec11 - CS 124/LINGUIST 180: From Click to edit...

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Click to edit Master subtitle style 1/10/09 Dan Jurafsky Lecture 11: Computational Lexical Semantics
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Slide from Chris Manning's 276 class Outline: Intro to Lexical Semantics Homonymy, Polysemy, Synonymy Thesaurus: WordNet Computational Lexical Semantics Word Similarity Thesaurus-based Distributional
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Slide from Chris Manning's 276 class Three Perspectives on Meaning 1. Lexical Semantics The meanings of individual words 2. Formal Semantics (or Compositional Semantics or Sentential Semantics) How those meanings combine to make meanings for individual sentences or utterances 3. Discourse or Pragmatics How those meanings combine with each other and with other facts about various kinds of context to make meanings for a text
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Slide from Chris Manning's 276 class Preliminaries What’s a word? Definitions we’ve used over the quarter: Types, tokens, stems, roots, etc. .. Lexeme : An entry in a lexicon consisting of a pairing of a form with a single meaning representation Lexicon : A collection of lexemes
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Slide from Chris Manning's 276 class Relationships between word Homonymy Polysemy Synonymy Antonymy Hypernomy Hyponomy Meronomy
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Slide from Chris Manning's 276 class First idea: The unit of meaning is called a Sense or wordsense One word “bank” can have multiple different meanings: “Instead, a bank can hold the investments in a custodial account in the client’s name” “But as agriculture burgeons on the east bank , the river will shrink even more” We say that a sense is a representation of one aspect of the meaning of a word. Thus bank here has two senses
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Slide from Chris Manning's 276 class Some more terminology Lemmas and wordforms A lexeme is an abstract pairing of meaning and form A lemma or citation form is the grammatical form that is used to represent a lexeme . Carpet is the lemma for carpets Dormir is the lemma for duermes . Specific surface forms carpets, sung, duermes are called wordforms The lemma bank has two senses: Instead, a bank can hold the investments in a custodial account in the client’s name But as agriculture burgeons on the east bank , the river will
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Slide from Chris Manning's 276 class Homonymy Homonymy: Lexemes that share a form Phonological, orthographic or both But have unrelated, distinct meanings Clear example: Bat (wooden stick-like thing) vs Bat (flying scary mammal thing) Or bank (financial institution) versus bank (riverside) Can be homophones, homographs, or both: Homophones: Write and right Piece and peace
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Slide from Chris Manning's 276 class Homonymy causes problems for Text-to-Speech Same orthographic form but different phonological form bass vs bass Information retrieval Different meanings same orthographic form QUERY: bat care Machine Translation Speech recognition Why?
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124.11.lec11 - CS 124/LINGUIST 180: From Click to edit...

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