Towardsatheoryoflexicals教学讲解课件

TowardsatheoryoflexicalsemanticsCogs3000Week7Towardsatheoryoflexicalse1GoalsofatheoryoflexicalsemanticsAtheoryoflexicalsemanticsneedsnotonlytoaccountforthemeaningofindividualwordsbuthowwordmeaningschangeincontextwithotherwords.Considerthemeaningofgoodinthephrasegoodfriend(<loyal,reliable>)Nowconsiderthemeaningofthesamewordinthephrasegoodloverorgoodmeal.Thereisachameleon-likequalitytothemeaningofsomewords,whichneedstobeaccountedfor.Goalsofatheoryoflexicals2LexicalsemanticsandPragmaticknowledgeThemeaningsofwordsaresaidtobestoredinthementaldictionary, alongwiththeirphonologicalandmorpho-syntacticfeatures.Lexicalknowledgeclearlyvariesfromspeakertospeaker.LanguagesalsovaryfromoneanotherinhowtheylexicalizeourknowledgeandperceptionoftheworldHence,lexicalsemanticsthoughintimatelyconnectedwithpragmatics(knowledgeoftheworld)isdistinctfromit.Lexicalknowledgeisconfinedtoknowledgeofwordmeaningsandwordusage.LexicalsemanticsandPragmati3TheproblemofpolysemyDictionarieshavemultiplemeaningslistedforanygivenwordandthemorecommontheword,themoremeaningsitwilltypicallyhavelistedagainstit.Meaningsof‘show’thatarefoundinthepocketOxford.Thecontextshavebeenscrambled.TheproblemofpolysemyDiction4Semanticanomalydetection…Anotherwaywemighttesttheadequacyofatheoryoflexicalsemantics.Itisthedetectionofanomalyintheactualexpressionwhichisofinteresttoushere,ratherthanhowtheanomalousutterancewasproduced.Semanticanomalydetection…An5Anothertest…Abilityofthesystemtogenerateacceptableparaphrasesforindividualwordsorphrasalexpressions.Toexpresscommonalitiesanddifferencesofmeaningbetweenverbalexpressionsthataresemanticallyrelated.abottleofwineversusajugofwhiskeyAnothertest…Abilityofthes6AfundamentalunresolvedproblemonhowtoapproachtheanalysisofwordandphrasemeaningsWhethersemantictheoryshouldbegroundedinlogicorinpsychology; insomeformalizedpropositionalcalculusoftruthconditionsforpossibleworlds, orinperceptualexperienceanditsinternalcognitiverepresentation.Theanswertothislongstandingcontroversymaylieinthelevelofanalysisadopted.Apropositionalcalculusisclearlymoreapplicabletosentence-levelsemanticanalysis.Thewayweperceiveobjectsintheworldisclearlyofcriticalinterestforthesemanticpropertiesofwords.Afundamentalunresolvedprobl7SemanticNetworksOneoftheearliestattemptstoconstructacomputationalmodeloflexicalsemanticswasundertakenbyRossQuillian(1968)Asystemambitiouslydubbed‘Theteachablelanguagecomprehender’(TLC)Aprogramdesignedtobecapableofbeingtaughtto‘comprehend’Englishtext.TheTLCenvisagedthelexiconasasemanticnetworkencodingbothworldknowledgeandthemeaningsofwords.SemanticNetworksOneoftheea8TheTLCQuillian’ssemanticnetworkisasymbolic,notaconnectionistnetwork.Thenodesofthenetworkrepresentconceptsorwords, thatarelinkedbyarcs,whichrepresentasmallnumberofrelationaltypes.Themeaningofawordmaybeexpressed,firstbyaccessingitsrootnodeinthenetworkandtraversingthenetworkelementstowhichthisnodeislinkedinaseriesofsteps.Aword’smeaningisdefinedbyotherwords,whosemeaningsaredefined,inturn,byotherwords.TheTLCQuillian’ssemanticnet9HowtheTLCrepresentsthepolysemouswordplantThesethreemeaningsofplantaredisjunctiveintheirusage.Thebasicmeaningofplant(PLANT1)andpointerstoitsalternativemeanings(PLANT2andPLANT3)areexpressedina‘planeofwordmemory’.HowtheTLCrepresentsthepol10SemanticnetworkforplantSemanticnetworkforplant11SemanticrepresentationsinTLCFourbasictypesofarclinkingnodesinasemanticnetworkInadditiontothebasiclogicalrelationsofdisjunction(OR)andconjunction(AND)Quillian’ssystemrecognizedasubordinate-superordinaterelation,whichothershavelabelled‘theISArelation’andwhichdefinesarelationshipofclassmembership(e.g.,dog-animal).Athirdtypeoflinkage,‘propertyattribution’linksonenodedirectlytoanother,declaringonenodeisapropertyofanothernode.Afourthtypeofcomplexlinkagebetweenthreenodesisusedtocapture‘thematicroles’: thethree-wayrelationshipthataverboraprepositiontypicallycontractswithnounsthattheyhead(e.g.,FROM3(foodgoal

airsource)).SemanticrepresentationsinTL12Quillian’sclassificationofarctypesissomewhatidiosyncratic.Heoverlookscertainkindsofsemanticrelationwidelyrecognizedinlexicalsemanticanalysis.Apart-wholerelationship,‘theHASrelation’,isusefulforrepresentingfunctionalcomponentsofmanyobjects(e.g.,cat:HAS(AND(fur,whiskers,eyes,etc.))Anothersemanticrelation,confinedtoverbs,butusefulforrelatingbasicverbmeaningstosynonymsthatelaborateamannerofexecutingthebasicverbisreferredtoastroponymy. walk:stroll,wander,march,etc.Quillian’sclassificationofa13TheproblemofsemanticdecompositionWhatrelationalmeanings(setofarctypes)shouldberegardedasprimitive?Quillian’sapproachtothisdifficulttheoreticalproblemispragmatic.Howwelldoesthesystemachieveitstaskofsimulatinghumanlexicalsemanticprocessinginrelationtotheeffortrequiredtobuildthenetwork?Verificationthroughtesting(engineeringapproach)Theproblemofsemanticdecomp14TestingyoursemanticprocessorFindthesemanticlinkagesbetweeneachwordpair.Expresseachlinkageinashortsentence.Testingyoursemanticprocesso15TestingtheTLCTestingtheTLC16HowTLCgeneratesitsresponsesGototherootnodeofeachwordinagivenpair.Traversethearcsofitsmemoryplane,lookingfornodesthatmatchtheothermemberofthepair.e.g.,GotoPLANT1;searchplaneofPLANT1forinstancesofLIVE.DothesameforLIVE1,lookingforinstancesofPLANT,keepingarecordofany‘intersections’thatarefound.Extendsearchforintersectionsfromtheprimarymeaningplaneofeachwordtoplanesatonearcremoved,alternatingbetweeneachmemberofthewordpairandkeepingarecordofthesearchpathforanylinkagesthatwereencountered.ThissearchofsemanticspaceQuilliancharacterizedasaformof‘spreadingactivation’HowTLCgeneratesitsresponse17HowTLCgeneratesitsresponsesThepathassociatedwitheach‘intersection’issavedintemporarymemoryuntilthesearchfinished.Finally,aseparateprogramwasusedto‘translate’eachintersectionpathintoa‘kindof,MeTarzan.YouJane’verbalexpression.Butwhatdoesthisdemonstrate?

AvariantoftheTuringtest.HowTLCgeneratesitsresponse18FromwordtosentencemeaningsToaccountforpolysemy,requirestheconceptualmachineryneededforexpressingsentencemeanings.Thepivotalroleoftheverb.Atheoryofthematicroleassignment.Johngavethelibraryabook<GIVE(Ag

John)(Thbook)(Golibrary)>Inmanystudiesofaphasiaandlanguageacquisition,theabilitytoassignthematicrolescorrectlyhasbeentakenasanoperationalcriterionofsentencecomprehension.Fromwordtosentencemeanings19TheproblemofsemanticparaphraseTheydidn’tletJohngooutoftheroom.TheypreventedJohnfromleavingtheroom.Postulateasmallsetofsemanticprimitives; andaparsingmechanism,orsetofinferentialrules.CharlesFillmore(1968)kill=<CAUSE(Ag__BECOME(NOT(ALIVE(Th__))))>Whatapproachescouldbetakentotheproblemofsemanticdecompositionofverbmeanings?Theproblemofsemanticparaph20ConceptualdependencytheoryRogerSchank(1975)Verbmeaningsareexpressibleascompositionalfunctionsofjust11semanticprimitivesortypesofACT.PROPEL,MOVE,INGEST,EXPEL,GRASP,PTRANS,ATRANS,MTRANS,MBUILD,SPEAK,INTENDConceptualDependencydiagramfor‘Johnateafrog.’ConceptualdependencytheoryR21Theconceptualdependencygraphisderivedfromsemanticinformationinlexicalitemsandfromsomegeneralrulesofconceptualstructureformation.Theconceptualdependencygrap22eatisanACToftypeINGEST,whichinvolvestheACTofMOVingsomeobjectYviaoneshandtoone’smouth.eatisanACToftypeINGEST,w23AugmentedConceptualDependencydiagramfor‘Johnateafrog.’

Thesemanticprimitivesofverbmeaningaregroundedinaconcretespatio-temporalworldofphysicalobjectsthatcollidewithoneanotherorareactivelypropelledthroughchangesofstateorlocationbywillfulbeings.Primitives,ATRANS,MTRANS,andMBUILDaremetaphoricalextensionsfromthephysicaltothementalworldofconceptsotherwiseapplicabletoatangibleworldofconcreteobjects.

AugmentedConceptualDependenc24CognitionasmetaphorMTRANSmeans‘totransferinformation’.HencetotellXaboutYistotransferknowledgefromonemetaphoricallocationinX’sdomaintothatofY.MBUILDmeans‘tocreateorcombinethoughts’.CognitiveGrammarhaselaboratedthesenotionsofmind-as-body-projection,throughtheconceptof

imageschemasandtheirroleinexplainingpatternsofpolysemy(seeLee,2002).CognitionasmetaphorMTRANSm25Evaluationofsymbolicmodelsoflexicalsemantics.Whatshouldaperformancemodelofwordmeaningshouldbeabletoaccomplish?Tohandlepolysemy(variationofwordmeaningwithphrasalcontext).Tocomputeobviousandnon-obviousrelationshipsofmeaningbetweenwordsandphrases.Toperformsemanticparaphrase.Thesegoalsweremoreexplicitlyandcomprehensivelyaddressedbythepreviousgenerationofsymbolicexpertsystemstylemodels(Quillian,1968,Schank,1975).Symbolicnetworksprovideadatastructuretosupportlexicalinference,whichenablestheconstructionofTuringtestsformodelsofwordcomprehension.Evaluationofsymbolicmodels26ProblemswithsymbolicnetworkmodelsoflexicalsemanticsFragilityofperformanceastheygrowmorecomplex;theirinflexibility.Symbolicsemanticnetworkshavenocapacitytolearnfromlanguageexperience.Experiencewithexpertsystemmodelsofsemanticmemoryalsodemonstratedthatafullyfledgedmodelofword-to-sentencelevelsemanticprocessingisinfeasibleatthepresenttime.Theartofthepossible…Problemswithsymbolicnetwork27InvestigatingsemanticstructuresWhendoesphrasalcontextstarttoexerciseaninfluenceonthesense-meaningofaword?Aresomesemanticrelationsmoreaccessibleormorerapidlycomputedon-linethanothers?Issemanticmemoryorganizedintorelativelydiscretemodulesorisitdistributedinahomogenoussystem?Towhatextentarethererelativelyindependent,modalityspecific,semanticsystemsthatservedifferentdomainslexicalusage?Doesthefactthatsomelexicalitemsrepresentclustersofhighlycorrelatedpropertiesorfeaturesrendertheirretrievalmorerobustthanotheritemswhosedistinguishingsemanticfeaturesaremoresparseandessentiallyuncorrelated?Investigatingsemanticstructu28Theroleofcontextinword-sensedisambiguation.Behaviouralstudiesofon-linelexicalretrieval,usingcross-modalsemanticprimingparadigm,Swinney(1979).Bothmeaningsofanambiguouswordsuchasbug(<insect>or<covertlisteningdevice>)areinitiallyactivated,regardlessofastronglybiassingdiscoursecontext: ‘Rumourhaditthatforyearsthebuildinghadbeenplaguedwithproblems.Themanwasnotsurprisedwhenhefoundseveralspiders,roaches,andotherbugs

inthecornerofhisroom’.Theroleofcontextinword-se29Swinney’sfindingsAlexicaldecisiontothecontextuallyinappropriatebutrelatedword‘spy’’wasfacilitatedjustasmuchasthecontextuallyappropriaterelatedword‘ant’.Whenadelaywasintroducedbypresentingtheprobewordthreesyllablesaftersubjectsheardtheambiguousprimeword,onlythecontextuallyappropriateprobe(ant)receivedasignificantprimingeffect.Whatdotheseresultssignify?Lexicalmeaningretrievalisaprocesswhichisinitiallyautonomousofcontexteffects.Swinney’sfindingsAlexicalde30Thesemanticprimingparadigmasawindowtoon-linewordmeaningretrieval.Somemethodologicalissues:thespecifictypeofprimingparadigmused,thepotentialimpactofnon-automaticorstrategicinfluencesuponprimingeffects,thedistinctionbetweenassociativeandsemanticeffectsinpriming.Thesemanticprimingparadigm31SemanticrelationtypesandassociativestrengthbetweenprimeandprobewordsMossetal.,1995,1997.Fourkindsofsemanticrelationwerecrossedwithatwolevelfactorofassociativelinkage(associatedvs.non-associated).Categorycoordinaterelationsarethemostfrequentlyusedinstudiesofsemanticpriming.Semanticrelationtypesandas32SemanticrelationsCategorycoordinationmaybeamorereadilyidentifiablesemanticrelationforpairsofnaturalobjectsthanartifactpairs… becausetaxonomicrelationsbasedonperceptualpropertiesaremoreapplicabletonaturalobjectsthantoartifacts.Functionalpropertiesmaybemoresalientforartifacts,whichtendtobeidentifiedbytheirusages.SemanticrelationsCategorycoo33SemanticrelationsCategoryspecificsemanticdeficitsforsubclassesofnaturalobjects(suchasfruitandvegetables)havebeenfoundinsomeaphasics(Warrington,1975) whichithasbeenarguedreflectmodularityofsemanticcategoriesfornaturalobjects.Mossetal.(1995)distinguishedbetweeninstrumentalandscriptedfunctionalrelations.SemanticrelationsCategoryspe34Results:associativeandsemanticprimingandtheeffectofprimetypeTherewasanappreciable‘boost’totheprimingeffectifprimeandprobewordswerealsoassociativelylinked.Inallbutthecaseofthe‘functionalscript’typeofsemanticrelation,therewasasignificantindependenteffectforsemanticallyrelatedprimes.Semanticprimingcannotbeattributedsolelytonormativeassociationstrength.Results:associativeandseman35However,Thestrengthofprimingeffectsassociatedwithdifferentkindsofprime-probesemanticrelationshipalsovariedwiththemodeofstimuluspresentation.Difficulttoarguethatanyhierarchyofaccessibilityorrapidityofactivationfordifferenttypesofsemanticrelationexists.However,Thestrengthofprimin36Someconclusions:SemanticPriming.Theimportanceofsemanticoverform-based(phonologicalororthographicsimilarity)primingeffectsappearstobepromotedbyuseofthecross-modalprimingparadigm.Welackabodyoffindingsonthetimecourseofactivationofsemanticpropertiestoindicatethattheparadigmreallyconstitutesawindowonlexicalsemanticprocessing.Semanticprimingeffectsrepresentmorethanactivationonthebasisofnormativeassociativestrengthbetweenprimeandprobe.Someconclusions:SemanticPri37BrainimagingstudiesoflexicalsemanticactivationThequestionsposedintheseinvestigationsunderstandablyhaveamorelocalist(localizationist)flavour.Studiesofnormalbrainactivityinlexicalprocessinghavebeeninfluencedbyrare,butstrikingcasereportsofcategory-specificsemanticdeficitsinaphasia.Neuro-imagingstudiesofsemanticorganizationinthenormalbrainarealsoinformedbyneurologicalmodelsofthedivisionofmentalorcomputationallabourinthebrain.Brainimagingstudiesoflexic38Thedivisionofmentallabourinthebrainbetweensensoryandmotorfunctions,episodicversusnon-episodicmemory,ordeclarativeversusproceduralknowledge(Ullman,2001)Modularorlocalistnotionsofbrainorganizationforperception,action,andmemoryaretakenasthestartingpointforneuro-linguisticmodelsoflexicalsemanticorganization.Thedivisionofmentallabour39Neuro-linguisticmodelsoflexicalsemanticorganizationNounsofhighimagability(‘pictureproducers’)maybeexpectedtohavemoreofaposterior(temporal-occipital)locusofrepresentationinthebrain.Verbs(‘actionwords’),moreofananterior(frontal)representation.Conflictingfindingshavebereportedintheimagingliteratureonthequestionofcerebrallocalizationfordifferentsemanticandgrammaticalcategoriesofwords.Neuro-linguisticmodelsoflex40Tyler,Stamatakis,Dick,Bright,FletcherandMossH(2003)UsedfMRItoexaminetheneuralactivationassociatedwithconceptualprocessingofnounsreferringtoanimalsandtoolsandforverbsreferringtotool-associatedactions(e.g.,drilling,painting)andbiologicalactions(e.g.,walking,jumping).Theyfoundthatobjectnamesandtheirassociatedactionsactivatedthesameareasofthetemporallobe,suggesting?...Namesforobjectsandactionsactivateasingledistributedsemanticnetwork.Noevidenceofcategoryspecificityforeitherobjectsoractions,andthesamepatternofactivationwasevokedfortheappearanceandmotionattributesofbothlivingandnonlivingcategories.Tyler,Stamatakis,Dick,Brigh41Anon-differentiated,distributednetworkforconceptualknowledgerepresentation?Tworecentstudiessuggestthatitmaybenecessarytoqualifytheconclusionwhenattentionispaidtosemanticandmorpho-syntacticattributesofthestimuliandthesubject’stask.AnfMRIstudyofsemanticjudgementswithinflectednounsandverbs(Tyler,Bright,Fletcher,&Stamatakis,2004).Subjectspresentedwithasemanticjudgementtaskinvolvingnounsandverbs,whereallitemswereexplicitlyinflectedforthatcategory(withregularplural{-s}orprogressive{-ing}marking).Anon-differentiated,distribu42Thesemanticjudgementtaskinvolveddecidingwhetherthethirdmemberoftripletbelongedordidnotbelongtoasemanticclassdeterminedbytheprecedingpair.Abaselineconditionwasincludedinwhichsubjectsjudgedwhetheratargetlettersequence(incapitals)matchedordidnotmatchtheprecedingletterpair.Thesemanticjudgementtaskinv43AnalysisThebaselinetaskfMRIactivationpatternsweresubtractedfromtheactivationpatternsobtainedfromthenounandverbjudgements,inordertoisolatethesemanticprocessingcomponentofthejudgementtaskfromtheorthographicprocessingcomponents.ThesubtractionofnounandverbactivationpatternsAnalysisThebaselinetaskfMRI44Results:theword–baselinesubtractionSeveralpeakactivationareaswereidentified.Theyclusteredintothreeorfourregions,predominantlyinthetemporallobeandtheleftfrontalgyrus,butwithsomelocatedsub-cortically.Thepatternofactivationwasconsistentwithawidelydistributednetworkforconceptualknowledgerepresentationandsemanticjudgement.Results:theword–baselines45Results:theverb–nounsubtractionTheverb-nounactivationareawasconfinedtoBroca’sarea(Brodmannareas44,45)andadjacentBrodmann’sarea47.Whydidtheverb-nounsubtractionyieldamuchmorerestrictiveandwell-definedactivationpatternthantheword-baselinesubtraction?Thenoun-verbsubtractionisahighlyfunctionallyrestrictivecomparison.Theword-baselinesubtractioninvolvesacontrastthatisfunctionallymuchgreater,butlesswelldefinedthanthenoun-verbsubtraction.Results:theverb–nounsubtr46Thewords–baselinesubtractionThewords–baselinesubtracti47Thenoun-verbsubtractionThenoun-verbsubtraction48ConclusionsTheresultsmaysaylittleaboutthelocuslexicalsemanticprocessinginthebrain,buttheyprovidecorroborationforevidencefromaphasiaofthecrucialroleofBroca’sareainmorpho-syntacticprocessing.Tyleretal.(2004)showthatthereissubstantialoverlapbetweentheareaofverbactivationintheleftinferiorfrontalgyrus(Broca’sarea)andthelesionsiteofpatientswhohavedifficultieswithregularverbalinflection.ConclusionsTheresultsmaysay49Moregenerally…Brainimagingstudiesoflexicalsemanticactivationhavenotyetyieldeddefinitiveevidenceoflocalizedormodularsemanticorganization.Techniquesofneuralimaginghavedevelopedtothepointwheretheynowapproachthelimitsofspatialresolution,beyondwhichindividualdifferencesinbrainanatomybegintoposeseriousrestrictionsoncross-braincomparisons.temporalresolutionisnowapproachingthepointwheresomeimagingtechniques(MEG)maybetakenasmeasuresofon-lineprocessing.Thechallengeisnowtobringgreatersophisticationtobearonthedesignofrelevantpsycholinguistictaskstobeusedinconjunctionwiththesepowerfulobservationaltools.Moregenerally…Brainimaging50TowardsatheoryoflexicalsemanticsCogs3000Week7Towardsatheoryoflexicalse51GoalsofatheoryoflexicalsemanticsAtheoryoflexicalsemanticsneedsnotonlytoaccountforthemeaningofindividualwordsbuthowwordmeaningschangeincontextwithotherwords.Considerthemeaningofgoodinthephrasegoodfriend(<loyal,reliable>)Nowconsiderthemeaningofthesamewordinthephrasegoodloverorgoodmeal.Thereisachameleon-likequalitytothemeaningofsomewords,whichneedstobeaccountedfor.Goalsofatheoryoflexicals52LexicalsemanticsandPragmaticknowledgeThemeaningsofwordsaresaidtobestoredinthementaldictionary, alongwiththeirphonologicalandmorpho-syntacticfeatures.Lexicalknowledgeclearlyvariesfromspeakertospeaker.LanguagesalsovaryfromoneanotherinhowtheylexicalizeourknowledgeandperceptionoftheworldHence,lexicalsemanticsthoughintimatelyconnectedwithpragmatics(knowledgeoftheworld)isdistinctfromit.Lexicalknowledgeisconfinedtoknowledgeofwordmeaningsandwordusage.LexicalsemanticsandPragmati53TheproblemofpolysemyDictionarieshavemultiplemeaningslistedforanygivenwordandthemorecommontheword,themoremeaningsitwilltypicallyhavelistedagainstit.Meaningsof‘show’thatarefoundinthepocketOxford.Thecontextshavebeenscrambled.TheproblemofpolysemyDiction54Semanticanomalydetection…Anotherwaywemighttesttheadequacyofatheoryoflexicalsemantics.Itisthedetectionofanomalyintheactualexpressionwhichisofinteresttoushere,ratherthanhowtheanomalousutterancewasproduced.Semanticanomalydetection…An55Anothertest…Abilityofthesystemtogenerateacceptableparaphrasesforindividualwordsorphrasalexpressions.Toexpresscommonalitiesanddifferencesofmeaningbetweenverbalexpressionsthataresemanticallyrelated.abottleofwineversusajugofwhiskeyAnothertest…Abilityofthes56AfundamentalunresolvedproblemonhowtoapproachtheanalysisofwordandphrasemeaningsWhethersemantictheoryshouldbegroundedinlogicorinpsychology; insomeformalizedpropositionalcalculusoftruthconditionsforpossibleworlds, orinperceptualexperienceanditsinternalcognitiverepresentation.Theanswertothislongstandingcontroversymaylieinthelevelofanalysisadopted.Apropositionalcalculusisclearlymoreapplicabletosentence-levelsemanticanalysis.Thewayweperceiveobjectsintheworldisclearlyofcriticalinterestforthesemanticpropertiesofwords.Afundamentalunresolvedprobl57SemanticNetworksOneoftheearliestattemptstoconstructacomputationalmodeloflexicalsemanticswasundertakenbyRossQuillian(1968)Asystemambitiouslydubbed‘Theteachablelanguagecomprehender’(TLC)Aprogramdesignedtobecapableofbeingtaughtto‘comprehend’Englishtext.TheTLCenvisagedthelexiconasasemanticnetworkencodingbothworldknowledgeandthemeaningsofwords.SemanticNetworksOneoftheea58TheTLCQuillian’ssemanticnetworkisasymbolic,notaconnectionistnetwork.Thenodesofthenetworkrepresentconceptsorwords, thatarelinkedbyarcs,whichrepresentasmallnumberofrelationaltypes.Themeaningofawordmaybeexpressed,firstbyaccessingitsrootnodeinthenetworkandtraversingthenetworkelementstowhichthisnodeislinkedinaseriesofsteps.Aword’smeaningisdefinedbyotherwords,whosemeaningsaredefined,inturn,byotherwords.TheTLCQuillian’ssemanticnet59HowtheTLCrepresentsthepolysemouswordplantThesethreemeaningsofplantaredisjunctiveintheirusage.Thebasicmeaningofplant(PLANT1)andpointerstoitsalternativemeanings(PLANT2andPLANT3)areexpressedina‘planeofwordmemory’.HowtheTLCrepresentsthepol60SemanticnetworkforplantSemanticnetworkforplant61SemanticrepresentationsinTLCFourbasictypesofarclinkingnodesinasemanticnetworkInadditiontothebasiclogicalrelationsofdisjunction(OR)andconjunction(AND)Quillian’ssystemrecognizedasubordinate-superordinaterelation,whichothershavelabelled‘theISArelation’andwhichdefinesarelationshipofclassmembership(e.g.,dog-animal).Athirdtypeoflinkage,‘propertyattribution’linksonenodedirectlytoanother,declaringonenodeisapropertyofanothernode.Afourthtypeofcomplexlinkagebetweenthreenodesisusedtocapture‘thematicroles’: thethree-wayrelationshipthataverboraprepositiontypicallycontractswithnounsthattheyhead(e.g.,FROM3(foodgoal

airsource)).SemanticrepresentationsinTL62Quillian’sclassificationofarctypesissomewhatidiosyncratic.Heoverlookscertainkindsofsemanticrelationwidelyrecognizedinlexicalsemanticanalysis.Apart-wholerelationship,‘theHASrelation’,isusefulforrepresentingfunctionalcomponentsofmanyobjects(e.g.,cat:HAS(AND(fur,whiskers,eyes,etc.))Anothersemanticrelation,confinedtoverbs,butusefulforrelatingbasicverbmeaningstosynonymsthatelaborateamannerofexecutingthebasicverbisreferredtoastroponymy. walk:stroll,wander,march,etc.Quillian’sclassificationofa63TheproblemofsemanticdecompositionWhatrelationalmeanings(setofarctypes)shouldberegardedasprimitive?Quillian’sapproachtothisdifficulttheoreticalproblemispragmatic.Howwelldoesthesystemachieveitstaskofsimulatinghumanlexicalsemanticprocessinginrelationtotheeffortrequiredtobuildthenetwork?Verificationthroughtesting(engineeringapproach)Theproblemofsemanticdecomp64TestingyoursemanticprocessorFindthesemanticlinkagesbetweeneachwordpair.Expresseachlinkageinashortsentence.Testingyoursemanticprocesso65TestingtheTLCTestingtheTLC66Ho