LanguageChapter 22Chapter 22 1Outline♦ Communication♦ Grammar♦ Syntactic analysis♦ ProblemsChapter 22 2Communication“Classical” view (pre-1953):language consists of sentences that are true/false (cf. logic)“Modern” view (post-1953):language is a form of actionWittgenstein (1953)Philosophical InvestigationsAustin (1962) How to Do Things with WordsSearle (1969) Speech ActsWhy?Chapter 22 3Communication“Classical” view (pre-1953):language consists of sentences that are true/false (cf. logic)“Modern” view (post-1953):language is a form of actionWittgenstein (1953)Philosophical InvestigationsAustin (1962) How to Do Things with WordsSearle (1969) Speech ActsWhy?Chapter 22 4Communication“Classical” view (pre-1953):language consists of sentences that are true/false (cf. logic)“Modern” view (post-1953):language is a form of actionWittgenstein (1953)Philosophical InvestigationsAustin (1962) How to Do Things with WordsSearle (1969) Speech ActsWhy?Chapter 22 5Communication“Classical” view (pre-1953):language consists of sentences that are true/false (cf. logic)“Modern” view (post-1953):language is a form of actionWittgenstein (1953)Philosophical InvestigationsAustin (1962) How to Do Things with WordsSearle (1969) Speech ActsWhy?To change the actions of other agentsChapter 22 6Speech actsSITUATIONSpeaker Utterance HearerSpeech acts achieve the speaker’s goals:Inform “There’s a pit in front of you”Query “Can you see the gold”Command “Pick it up”Promise “I’ll share the gold with you”Acknowledge “OK”Speech act planning requires knowledge of– Situation– Semantic and syntactic conventions– Hearer’s goals, knowledge base, and rationalityChapter 22 7Stages in communication (informing)Intention S wants to inform H that PGeneration S selects words W to express PSynthesis S utters words WPerception H perceives W0Analysis H infers possible meanings P1, . . . PnDisambiguation H infers intended meaning PiIncorporation H incorporates Piinto KBHow could this go wrong?Chapter 22 8Stages in communication (informing)Intention S wants to inform H that PGeneration S selects words W to express PSynthesis S utters words WPerception H perceives W0Analysis H infers possible meanings P1, . . . PnDisambiguation H infers intended meaning PiIncorporation H incorporates Piinto KBHow could this go wrong?– Insincerity (S doesn’t believeP )– Speech wreck ignition failure– Ambiguous utterance– Differing understanding of current situationChapter 22 9GrammarVervet monkeys, antelopes etc. use isolated symbols for sentences⇒ restricted set of communicable propositions, no generative capacity(Chomsky (1957): Syntactic Structures)Grammar specifies the compositional structure of complex messagese.g., speech (linear), text (linear), music (two-dimensional)Aformal language is a set of strings of terminal symbolsEach string in the language can be analyzed/generated by the grammarThe grammar is a set ofrewrite rules, e.g.,S → NP VPArticle → the | a | an | . . .HereS is the sentence symbol, NP and VP are nonterminalsChapter 22 10Grammar typesRegular: nonterminal → terminal[nonterminal ]S → aSS → ΛContext-free: nonterminal → anythingS → aS bContext-sensitive: more nonterminals on right-hand sideASB → AAaBBRecursively enumerable: no constraintsRelated to Post systems and Kleene systems of rewrite rulesNatural languages probably context-free, parsable in real time!Chapter 22 11Wumpus lexiconNoun → stench | breeze | glitter | nothing| wumpus | pit | pits | gold | east | . . .Verb → is | see | smell | shoot | f eel | stinks| go | grab | carry | kill | turn | . . .Adjective → right | left | east | south | back | smelly | . . .Adverb → here | there | nearby | ahead| right | left | east | south | back | . . .Pronoun → me | you | I | it | . . .Name → John | Mary | Boston | UCB | P AJC | . . .Article → the | a | an | . . .Preposition → to | in | on | near | . . .Conjunction → and | or | but | . . .Digit → 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9Divided intoclosed and open classesChapter 22 12Wumpus lexiconNoun → stench | breeze | glitter | nothing| wumpus | pit | pits | gold | east | . . .Verb → is | see | smell | shoot | f eel | stinks| go | grab | carry | kill | turn | . . .Adjective → right | left | east | south | back | smelly | . . .Adverb → here | there | nearby | ahead| right | left | east | south | back | . . .Pronoun → me | you | I | it |S/HE | Y0ALL . . .Name → John | Mary | Boston | UCB | P AJC | . . .Article → the | a | an | . . .Preposition → to | in | on | near | . . .Conjunction → and | or | but | . . .Digit → 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9Divided intoclosed and open classesChapter 22 13Wumpus grammarS → NP VP I + feel a breeze| S Conjunction S I feel a breeze + and + I smell a wumpusNP → Pronoun I| Noun pits| Article Noun the + wumpus| Digit Digit 3 4| NP PP the wumpus + to the east| NP RelClause the wumpus + that is smellyVP → Verb stinks| VP NP feel + a breeze| VP Adjective is + smelly| VP PP turn + to the east| VP Adverb go + aheadPP → Preposition NP to + the eastRelClause → that VP that + is smellyChapter 22 14Grammaticality judgementsFormal language L1may differ from natural language L2L1L2false positivesfalse negativesAdjusting L1to agree with L2is a learning problem!* the gold grab the wumpus* I smell the wumpus the goldI give the wumpus the gold* I donate the wumpus the goldIntersubjective agreement somewhat reliable, independent of semantics!Real grammars 10–500 pages, insufficient even for “proper” EnglishChapter 22 15Parse treesExhibit the grammatical structure of a sentenceI shoot the wumpusChapter 22 16Parse treesExhibit the grammatical structure of a sentenceI shoot the wumpusPronoun Verb Article NounChapter 22 17Parse treesExhibit the grammatical structure of a sentenceI shoot the wumpusPronoun Verb Article NounNP VP NPChapter 22 18Parse treesExhibit the grammatical structure of a sentenceI shoot the wumpusPronoun Verb Article NounNP VP NPVPChapter 22 19Parse treesExhibit the grammatical structure of a sentenceI shoot the wumpusPronoun Verb Article NounNP VP NPVPSChapter 22 20Syntax in NLPMost view syntactic structure as an essential step towards meaning;“Mary hit John” 6= “John hit Mary”“And since I was not informed—as a matter of fact, since I did not knowthat there were excess funds until we, ourselves, in that checkup after thewhole thing