ge langua communica

CommunicationandLanguage

Chapter22

Chapter221

Outline

♦Communication

♦Grammar

♦Syntacticanalysis

♦Problems

Chapter222

Communication

“Classical”view(pre-1953):languageconsistsofsentencesthataretrue/false(cf.logic)

“Modern”view(post-1953):languageisaformofaction

Wittgenstein(1953)PhilosophicalInvestigations

Austin(1962)HowtoDoThingswithWords

Searle(1969)SpeechActs

Why?

Chapter223

Communication






Why?

Chapter224

Communication






Why?

Chapter225

Communication






Why?

Tochangetheactionsofotheragents

Chapter226

Speechacts

SITUATION

SpeakerUtteranceHearer

Speechactsachievethespeaker’sgoals:Inform“There’sapitinfrontofyou”Query“Canyouseethegold?”Command“Pickitup”Promise“I’llsharethegoldwithyou”Acknowledge“OK”

Speechactplanningrequiresknowledgeof–Situation–Semanticandsyntacticconventions–Hearer’sgoals,knowledgebase,andrationality

Chapter227

Stagesincommunication(informing)

IntentionSwantstoinformHthatP

GenerationSselectswordsWtoexpressPincontextC

SynthesisSutterswordsW

PerceptionHperceivesW′incontextC

′

AnalysisHinferspossiblemeaningsP1,...Pn

DisambiguationHinfersintendedmeaningPi

IncorporationHincorporatesPiintoKB

Howcouldthisgowrong?

Chapter228

Stagesincommunication(informing)

IntentionSwantstoinformHthatP

GenerationSselectswordsWtoexpressPincontextC

SynthesisSutterswordsW

PerceptionHperceivesW′incontextC

′

AnalysisHinferspossiblemeaningsP1,...Pn

DisambiguationHinfersintendedmeaningPi

IncorporationHincorporatesPiintoKB

Howcouldthisgowrong?–Insincerity(Sdoesn’tbelieveP)–Speechwreckignitionfailure–Ambiguousutterance–Differingunderstandingofcurrentcontext(C6=C

′)

Chapter229

Grammar

Vervetmonkeys,antelopesetc.useisolatedsymbolsforsentences⇒restrictedsetofcommunicablepropositions,nogenerativecapacity

(Chomsky(1957):SyntacticStructures)

Grammarspecifiesthecompositionalstructureofcomplexmessagese.g.,speech(linear),text(linear),music(two-dimensional)

Aformallanguageisasetofstringsofterminalsymbols

Eachstringinthelanguagecanbeanalyzed/generatedbythegrammar

Thegrammarisasetofrewriterules,e.g.,

S→NPVP

Article→the|a|an|...

HereSisthesentencesymbol,NPandVParenonterminals

Chapter2210

Grammartypes

Regular:nonterminal→terminal[nonterminal]

S→aS

S→Λ

Context-free:nonterminal→anything

S→aSb

Context-sensitive:morenonterminalsonright-handside

ASB→AAaBB

Recursivelyenumerable:noconstraints

RelatedtoPostsystemsandKleenesystemsofrewriterules

Naturallanguagesprobablycontext-free,parsableinrealtime!

Chapter2211

Grammaticalityjudgements

FormallanguageL1maydifferfromnaturallanguageL2

L1L2

false positives

false negatives

AdjustingL1toagreewithL2isalearningproblem!

*thegoldgrabthewumpus*Ismellthewumpusthegold

Igivethewumpusthegold*Idonatethewumpusthegold

Intersubjectiveagreementsomewhatreliable,independentofsemantics!Realgrammars10–500pages,insufficientevenfor“proper”English

Chapter2215

Parsetrees

Exhibitthegrammaticalstructureofasentence

Ishootthewumpus

Chapter2216

Parsetrees


Ishootthewumpus

PronounVerbArticleNoun

Chapter2217

Parsetrees


Ishootthewumpus


NPVPNP

Chapter2218

Parsetrees


Ishootthewumpus


NPVPNP

VP

Chapter2219

Parsetrees


Ishootthewumpus


NPVPNP

VP

S

Chapter2220

SyntaxinNLP

Mostviewsyntacticstructureasanessentialsteptowardsmeaning;“MaryhitJohn”6=“JohnhitMary”

“AndsinceIwasnotinformed—asamatteroffact,sinceIdidnotknowthattherewereexcessfundsuntilwe,ourselves,inthatcheckupafterthewholethingblewup,andthatwas,ifyou’llremember,thatwastheincidentinwhichtheattorneygeneralcametomeandtoldmethathehadseenamemothatindicatedthattherewerenomorefunds.”

Chapter2221

SyntaxinNLP

Mostviewsyntacticstructureasanessentialsteptowardsmeaning;“MaryhitJohn”6=“JohnhitMary”

“AndsinceIwasnotinformed—asamatteroffact,sinceIdidnotknowthattherewereexcessfundsuntilwe,ourselves,inthatcheckupafterthewholethingblewup,andthatwas,ifyou’llremember,thatwastheincidentinwhichtheattorneygeneralcametomeandtoldmethathehadseenamemothatindicatedthattherewerenomorefunds.”

“Wouldn’tthesentence’IwanttoputahyphenbetweenthewordsFishandAndandAndandChipsinmyFish-And-Chipssign’havebeenclearerifquotationmarkshadbeenplacedbeforeFish,andbetweenFishandand,andandandAnd,andAndandand,andandandAnd,andAndandand,andandandChips,aswellasafterChips?”

Chapter2222

Context-freeparsing

Bottom-upparsingworksbyreplacinganysubstringthatmatchesRHSofarulewiththerule’sLHS

Efficientalgorithms(e.g.,chartparsing,Section22.3)O(n3)forcontext-free,

runatseveralthousandwords/secforrealgrammars

Context-freeparsing≡Booleanmatrixmultiplication(Lee,2002)⇒unlikelytofindfasterpracticalalgorithms

Chapter2223

Logicalgrammars

BNFnotationforgrammarstoorestrictive:–difficulttoadd“sideconditions”(numberagreement,etc.)–difficulttoconnectsyntaxtosemantics

Idea:expressgrammarrulesaslogic

X→YZbecomesY(s1)∧Z(s2)⇒X(Append(s1,s2))X→wordbecomesX([“word”])X→Y|ZbecomesY(s)⇒X(s)Z(s)⇒X(s)

Here,X(s)meansthatstringscanbeinterpretedasanX

Chapter2224

Logicalgrammarscontd.

Nowit’seasytoaugmenttherules

NP(s1)∧EatsBreakfast(Ref(s1))∧VP(s2)

⇒NP(Append(s1,[“who”],s2))

NP(s1)∧Number(s1,n)∧VP(s2)∧Number(s2,n)

⇒S(Append(s1,s2))

Parsingisreducedtologicalinference:Ask(KB,S([“I”“am”“a”“wumpus”]))

(Canaddextraargumentstoreturntheparsestructure,semantics)

Generationsimplyrequiresaquerywithuninstantiatedvariables:Ask(KB,S(x))

Ifweaddargumentstononterminalstoconstructsentencesemantics,NLPgenerationcanbedonefromagivenlogicalsentence:

Ask(KB,S(x,At(Robot,[1,1]))

Chapter2225

Reallanguage

RealhumanlanguagesprovidemanyproblemsforNLP:

♦ambiguity

♦anaphora

♦indexicality

♦vagueness

♦discoursestructure

♦metonymy

♦metaphor

♦noncompositionality

Chapter2226

Ambiguity

Squadhelpsdogbitevictim

Chapter2227

Ambiguity

SquadhelpsdogbitevictimHelicopterpoweredbyhumanflies

Chapter2228

Ambiguity

SquadhelpsdogbitevictimHelicopterpoweredbyhumanfliesAmericanpushesbottleupGermans

Chapter2229

Ambiguity

SquadhelpsdogbitevictimHelicopterpoweredbyhumanfliesAmericanpushesbottleupGermansIatespaghettiwithmeatballs

Chapter2230

Ambiguity


salad

Chapter2231

Ambiguity


saladabandon

Chapter2232

Ambiguity


saladabandonafork

Chapter2233

Ambiguity


saladabandonaforkafriend

Chapter2234

Ambiguity


saladabandonaforkafriend

Ambiguitycanbelexical(polysemy),syntactic,semantic,referential

Chapter2235

Anaphora

Usingpronounstoreferbacktoentitiesalreadyintroducedinthetext

AfterMaryproposedtoJohn,theyfoundapreacherandgotmarried.

Chapter2236

Anaphora



Forthehoneymoon,theywenttoHawaii

Chapter2237

Anaphora




MarysawaringthroughthewindowandaskedJohnforit

Chapter2238

Anaphora




MarysawaringthroughthewindowandaskedJohnforit

Marythrewarockatthewindowandbrokeit

Chapter2239

Indexicality

Indexicalsentencesrefertoutterancesituation(place,time,S/H,etc.)

Iamoverhere

Whydidyoudothat?

Chapter2240

Metonymy

Usingonenounphrasetostandforanother

I’vereadShakespeare

Chryslerannouncedrecordprofits

ThehamsandwichonTable4wantsanotherbeer

Chapter2241

Metaphor

“Non-literal”usageofwordsandphrases,oftensystematic:

I’vetriedkillingtheprocessbutitwon’tdie.Itsparentkeepsitalive.

Chapter2242

Noncompositionality

basketballshoes

Chapter2243

Noncompositionality

basketballshoesbabyshoes

Chapter2244

Noncompositionality

basketballshoesbabyshoesalligatorshoes

Chapter2245

Noncompositionality

basketballshoesbabyshoesalligatorshoesdesignershoes

Chapter2246

Noncompositionality

basketballshoesbabyshoesalligatorshoesdesignershoesbrakeshoes

Chapter2247

Noncompositionality


redbook

Chapter2248

Noncompositionality


redbookredpen

Chapter2249

Noncompositionality


redbookredpenredhair

Chapter2250

Noncompositionality


redbookredpenredhairredherring

Chapter2251

Noncompositionality



smallmoon

Chapter2252

Noncompositionality



smallmoonlargemolecule

Chapter2253

Noncompositionality



smallmoonlargemoleculemerechild

Chapter2254

Noncompositionality



smallmoonlargemoleculemerechildallegedmurderer

Chapter2255

Noncompositionality



smallmoonlargemoleculemerechildallegedmurdererrealleather

Chapter2256

Noncompositionality



smallmoonlargemoleculemerechildallegedmurdererrealleatherartificialgrass

Chapter2257

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