Chapter 22 - Communication

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# Chapter 22 - Communication - PowerPoint PPT Presentation

Chapter 22 - Communication. April 8, 2004. 22.5 – Semantic Interpretation. Uses First Order Logic as the representation language Compositional Semantics Instead of NP  Digit Digit NP([x, y])  Digit(x) Digit(y), x and y are associated semantics

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### Chapter 22 - Communication

April 8, 2004

22.5 – Semantic Interpretation
• Uses First Order Logic as the representation language
• Compositional Semantics
• Instead of NP  Digit Digit
• NP([x, y])  Digit(x) Digit(y), x and y are associated semantics
• another application of DCG; definite clause grammar
Examples
• Applied to arithmetic
• Figure 22.14
• Figure 22.15
• Applied to English
• Figure 22.16
• Figure 22.17
Augmentations
• Time and tense
• use event calculus
• for example, Verb( λx λy e Î Loves(x,y) ^ After(Now, e)  loved
• Quasi-Logical Form [a a Î Agents]
• Somewhere between syntax and semantics
• Can represent different possibilities succinctly
• Figure 22.18
• Pragmatics can resolve indexicals. “We are in CS 536 today”.
22.6 – Ambiguity and Disambiguation
• “Portable toilet bombed; police have nothing to go on”
• Lexical, e.g. “class”
• Syntactic, e.g. “The man gave the gift with a smile”. “The man saw the boy with the smile”.
• Semantic
•  m, x, e [x = MSU ^ e Î Announce(m) ^ After(Now, e) ^ Metonymy(m) ]
• Metaphor. Indirect comparison. For example, the notion that more is up.
Disambiguation
• argmax intent Likelihood ( intent | words, situation)
• Knowledge Sources
• World Model
• Mental Model
• Language Model
• Acoustic Model
22.7 – Discourse Understanding
• Reference resolution. Relies on syntax, semantics and pragmatics. For example, “he”.
• Structure of coherent discourse.
• Figure 22.21. Coherence Relations.
22.8 – Grammar Induction
• SEQUITUR (1997)
• No pair of adjacent symbols should appear more than once in the grammar
• Every rule should be used at least twice
• Figure 22.22