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CPE 480 Natural Language Processing. Lecture 6: Semantics--From words to sentences to idioms Asst. Prof. Nuttanart Facundes, Ph.D. Theories of Meaning. Words have different meaning, depending on the context in which they are used What is the meaning of a word?

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cpe 480 natural language processing

CPE 480 Natural Language Processing

Lecture 6: Semantics--From words to sentences to idioms

Asst. Prof. Nuttanart Facundes, Ph.D.

theories of meaning
Theories of Meaning
  • Words have different meaning, depending on the context in which they are used
    • What is the meaning of a word?
    • How can we represent the meaning?
    • What formalisms can be used?
4 representation approaches
4 Representation Approaches
  • First-Order Predicate Calculus
  • Semantic Networks
  • Conceptual Dependencies
  • Frame-Based Representations
correspondences between representations
Correspondences between representations
  • They all share a common foundation:

 meaning representation consists of structures composed of sets of symbols

Symbol Structures

 are objects and relations among objects

meaning structure of language
Meaning structure of language
  • Various ways by which human language conveys meaning
    • Form-meaning associations
    • Word-order regularities
    • Sense systems
    • Conjunctions and quantifiers
    • Predicate-argument structure
problems with fopc
Problems with FOPC
  • Hard to represent beliefs
  • For example: I believe that Mary ate British food.
principle of compositionality frege
Principle of Compositionality (Frege)
  • The meaning of a sentence is composed by the meaning of its parts
semantic augmentations to context free grammars
Semantic Augmentations to Context-Free Grammars
  • Augmenting context-free grammar rules with semantic attachments
  • Attachments = Instructions that specify how to compute the meaning representation of a construction from the meanings of its consistent parts
different sentences
Different Sentences
  • Declarative: Flight 487 serves lunch.
  • Imperative: Serve lunch.
  • Yes/No Questions: Does Flight 207 serve lunch?
  • Wh-Questions: Which flights serve lunch?
the role of sentences
The Role of Sentences
  • Declarative  intended to convey factual information
  • Imperative  request for an action
  • Yes/No Questions  request for affirmative/negative answer
  • Wh-Questions  request for information
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