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 –Figure Applied to English –Figure –Figure 22.17

Augmentations Time and tense –use event calculus –for example, Verb( λx λy e  Loves(x,y) ^ After(Now, e)  loved Quasi-Logical Form [  a a  Agents] –Somewhere between syntax and semantics –Can represent different possibilities succinctly –Figure 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  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 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