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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
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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
Metonymy. One object stands for another. For example, “MSU said”. • 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