Communication Classical view (pre-1953): language consists of - PDF document

Communication “Classical” view (pre-1953): language consists of sentences that are true/false (cf. logic) “Modern” view (post-1953): Communication and Language language is a form of action Wittgenstein (1953) Philosophical Investigations Austin (1962) How to Do Things with Words Searle (1969) Speech Acts Chapter 22 Why utter? Chapter 22 1 Chapter 22 4 Outline Communication ♦ Communication “Classical” view (pre-1953): language consists of sentences that are true/false (cf. logic) ♦ Grammar “Modern” view (post-1953): ♦ Syntactic analysis language is a form of action ♦ Problems Wittgenstein (1953) Philosophical Investigations Austin (1962) How to Do Things with Words Searle (1969) Speech Acts Why utter? Chapter 22 2 Chapter 22 5 Communication Communication “Classical” view (pre-1953): “Classical” view (pre-1953): language consists of sentences that are true/false (cf. logic) language consists of sentences that are true/false (cf. logic) “Modern” view (post-1953): “Modern” view (post-1953): language is a form of action language is a form of action Wittgenstein (1953) Philosophical Investigations Wittgenstein (1953) Philosophical Investigations Austin (1962) How to Do Things with Words Austin (1962) How to Do Things with Words Searle (1969) Speech Acts Searle (1969) Speech Acts Why utter? Why utter? To change the actions of other agents Chapter 22 3 Chapter 22 6

Speech acts Grammar Vervet monkeys, antelopes, etc. use isolated symbols for sentences SITUATION ⇒ restricted set of communicable propositions, no generative capacity Speaker Utterance Hearer (Chomsky (1957): Syntactic Structures ) Grammar specifies the compositional structure of complex messages e.g., speech (linear), text (linear), music (two-dimensional) Speech acts achieve the speaker’s goals: A formal language is a set of strings of terminal symbols Inform “There’s a pit in front of you” “Can you see the gold?” Query Each string in the language can be analyzed/generated by the grammar Command “Pick it up” “I’ll share the gold with you” Promise The grammar is a set of rewrite rules, e.g., Acknowledge “OK” S → NP VP Speech act planning requires knowledge of Article → the | a | an | . . . – Situation Here S is the sentence symbol, NP , VP , and Article are nonterminals – Semantic and syntactic conventions – Hearer’s goals, knowledge base, and rationality Chapter 22 7 Chapter 22 10 Stages in communication (informing) Grammar types Regular: nonterminal → terminal [ nonterminal ] S wants to inform H that P Intention Generation S selects words W to express P in context C S → a S Synthesis S utters words W S → Λ H perceives W ′ in context C ′ Context-free: nonterminal → anything Perception Analysis H infers possible meanings P 1 , . . . P n S → a S b Disambiguation H infers intended meaning P i Incorporation H incorporates P i into KB Context-sensitive: more nonterminals on right-hand side How could this go wrong? ASB → AA a BB Recursively enumerable: no constraints Natural languages probably context-free, parsable in real time! Chapter 22 8 Chapter 22 11 Stages in communication (informing) Wumpus lexicon Noun → stench | breeze | glitter | nothing S wants to inform H that P Intention Generation S selects words W to express P in context C | wumpus | pit | pits | gold | east | . . . Synthesis S utters words W Verb → is | see | smell | shoot | feel | stinks | go | grab | carry | kill | turn | . . . H perceives W ′ in context C ′ Perception Adjective → right | left | east | south | back | smelly | . . . Analysis H infers possible meanings P 1 , . . . P n Adverb → here | there | nearby | ahead Disambiguation H infers intended meaning P i | right | left | east | south | back | . . . Incorporation H incorporates P i into KB Pronoun → me | you | I | it | . . . How could this go wrong? Name → John | Mary | Boston | UCB | P AJC | . . . – Insincerity (S doesn’t believe P ) Article → the | a | an | . . . – Speech wreck ignition failure Preposition → to | in | on | near | . . . – Ambiguous utterance Conjunction → and | or | but | . . . – Differing understanding of current context ( C � = C ′ ) Chapter 22 9 Chapter 22 12

Wumpus lexicon Wumpus lexicon Noun → stench | breeze | glitter | nothing Noun → stench | breeze | glitter | nothing | wumpus | pit | pits | gold | east | . . . | wumpus | pit | pits | gold | east | . . . Verb → is | see | smell | shoot | feel | stinks Verb → is | see | smell | shoot | feel | stinks | go | grab | carry | kill | turn | . . . | go | grab | carry | kill | turn | google . . . Adjective → right | left | east | south | back | smelly | . . . Adjective → right | left | east | south | back | smelly | . . . Adverb → here | there | nearby | ahead Adverb → here | there | nearby | ahead | right | left | east | south | back | . . . | right | left | east | south | back | . . . Pronoun → me | you | I | it | . . . Pronoun → me | you | I | it | . . . Name → John | Mary | Boston | UCB | P AJC | . . . Name → John | Mary | Boston | UCB | P AJC | Google . . . Article → the | a | an | . . . Article → the | a | an | . . . Preposition → to | in | on | near | . . . Preposition → to | in | on | near | . . . Conjunction → and | or | but | . . . Conjunction → and | or | but | . . . Digit → 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 Open classes are large, unbounded, change very fast Closed classes are small, bounded, change very slowly Chapter 22 13 Chapter 22 16 Wumpus lexicon Wumpus grammar S → NP VP I + feel a breeze Noun → stench | breeze | glitter | nothing | I feel a breeze + and + I smell a wumpus S Conjunction S | wumpus | pit | pits | gold | east | . . . NP → Pronoun I Verb → is | see | smell | shoot | feel | stinks | Noun pits | go | grab | carry | kill | turn | . . . | Article Noun the + wumpus Adjective → right | left | east | south | back | smelly | . . . | 3 4 Digit Digit Adverb → here | there | nearby | ahead | NP PP the wumpus + to the east | right | left | east | south | back | . . . | NP RelClause the wumpus + that is smelly Pronoun → me | you | I | it | thou | y ′ all . . . VP → Verb stinks Name → John | Mary | Boston | UCB | P AJC | . . . | feel + a breeze VP NP Article → the | a | an | . . . | VP Adjective is + smelly Preposition → to | in | on | near | . . . | VP PP turn + to the east Conjunction → and | or | but | . . . | go + ahead VP Adverb Digit → 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 PP → Preposition NP to + the east RelClause → that VP that + is smelly Closed classes are small, bounded, change very slowly Chapter 22 14 Chapter 22 17 Wumpus lexicon Grammaticality judgements Formal language L 1 may differ from natural language L 2 Noun → stench | breeze | glitter | nothing | wumpus | pit | pits | gold | east | . . . L 1 L 2 Verb → is | see | smell | shoot | feel | stinks false false | go | grab | carry | kill | turn | . . . positives negatives Adjective → right | left | east | south | back | smelly | . . . Adverb → here | there | nearby | ahead | right | left | east | south | back | . . . Pronoun → me | you | I | it | . . . Adjusting L 1 to agree with L 2 is a learning problem! Name → John | Mary | Boston | UCB | P AJC | . . . Article → the | a | an | . . . * the gold grab the wumpus * I smell the wumpus the gold Preposition → to | in | on | near | . . . I give the wumpus the gold Conjunction → and | or | but | . . . * I donate the wumpus the gold Open classes are large, unbounded, change very fast Intersubjective agreement somewhat reliable, independent of semantics! Real grammars 10–500 pages, insufficient even for “proper” English Chapter 22 15 Chapter 22 18

Parse trees Parse trees Exhibit the grammatical structure of a sentence Exhibit the grammatical structure of a sentence VP NP VP NP Pronoun Verb Article Noun I shoot the wumpus I shoot the wumpus Chapter 22 19 Chapter 22 22 Parse trees Parse trees Exhibit the grammatical structure of a sentence Exhibit the grammatical structure of a sentence S VP NP VP NP Pronoun Verb Article Noun Pronoun Verb Article Noun I shoot the wumpus I shoot the wumpus Chapter 22 20 Chapter 22 23 Parse trees Parse trees Exhibit the grammatical structure of a sentence Exhibit the grammatical structure of a sentence S VP NP VP NP NP VP NP Pronoun Verb Article Noun Pronoun Verb Article Noun I shoot the wumpus I shoot the wumpus Efficient CFG algorithms (e.g., chart parsing, Section 22.3) O ( n 3 ) Chapter 22 21 Chapter 22 24