Struktura
Therepresentationofknowledgeisadescriptionofknowledge,orasetofconventionsonknowledge,adatastructureacceptabletocomputersfordescribingknowledge.Inasense,representationcanberegardedasasynthesisofdatastructureanditsprocessingmechanism:representation=datastructure+processingmechanism.Therefore,knowledgerepresentationinESisaseriesoftechnicalmeansthatcancompletethecomputerprocessingofexpertknowledgeinES.Thecommononesareproductionrules,semanticweb,framemethodandsoon.
Představuje předmět
Knowledgeisthecorrectconclusionobtainedbytheinformationreceiverthroughtherefiningandreasoningoftheinformation;itisthehuman'sunderstandingofthenaturalworld,humansociety,andthelawofthinkingandmovement.Recognitionandmasteryaretherecombinationandsystematicinformationcollectionofthehumanbrainthroughthinking.
InKR,themeaningofknowledgeisdifferentfromthemeaningofknowledgegenerallyknowntous.Itreferstoconcepts,eventsandprocessesexpressedinacertainstructuredway.Therefore,inKR,notallknowledgeindailylifecanbeembodied,butonlywhenthescopeandstructurearelimited,theknowledgethathasbeencodedandtransformedcanbecometheknowledgeinKR.TheknowledgeinKRgenerallyhasthefollowingcategories:
Conceptsabouttheobjectsofinterestintherealworld,thatis,usedtodescribetheabstractandsummarizedconceptsintherealworld.
Abouteventsthatoccurintherealworld,thebehaviorsandstatesofrelatedobjects,etc.,thatistosay,therearenotonlystaticconcepts,butalsodynamicinformation.
Knowledgeabouttheprocess,thatis,notonlythedescriptionofthecurrentstateandbehavior,butalsothedescriptionofthechangesinitsdevelopmentanditsrelatedconditions,causality,etc.
Metaznalosti, tedy znalosti o znalostech, například včetně znalostí o použití znalostí.
Metoda
Throughthejointeffortsofdomesticandforeignscholars,manyknowledgerepresentationmethodshavebeenstudiedindepth,andthemostusedknowledgerepresentationmethodsmainlyincludethefollowingknowledgerepresentationmethods.
(1) Logická notace
Logicalnotationexpressesthesubjectandobjectofactionsintheformofpredicates,whichisanarrativeknowledgerepresentationmethod.Usinglogicalformulas,peoplecandescribeobjects,properties,conditions,andrelationships.Itismainlyusedfortheproofofautomatictheorems.Logicalnotationismainlydividedintopropositionallogicandpredicatelogic.
Logicalrepresentationstudiestheimplicationrelationshipbetweenhypothesisandconclusion,thatis,thelawofreasoningwithlogicalmethods.Itcanbeseenasasimplifiedformofnaturallanguage.Becauseofitsaccuracyandunambiguousness,itiseasytounderstandandoperatebycomputers,andatthesametimeitissimilartonaturallanguage.
Propositionallogicisakindofmathematicallogic.Mathematicallogicusesformallanguage(logicalsymbollanguage)forprecise(withoutambiguity)descriptionandmathematicalresearch.Whatwearemostfamiliarwithistherepresentationofunknownsinmathematics.Example:Usepropositionallogictoexpressthefollowingknowledge:
Jestližeajesudéčíslo,pak2jesudéčíslo.
Řešení:Definujte tvrzení následovně:P:ajesudéčíslo;Q:a2jesudéčíslo,pak:původní znalost je vyjádřenajako:P→Q
ThepredicatelogicisequivalenttothefunctioninmathematicsExpress.Example:Usepredicatelogictoexpressknowledge:naturalnumbersareallintegersgreaterthanorequaltozero
Řešení:definujte predikát takto:N(x):xijepřirozené číslo;I(x):xisancelé číslo;GZ(x):xiječíslo větší než rovné nule.Takže původní znalost je vyjádřena jako:(∀x)(N(x)(GZ(x)∧I(x)),∀( x) je univerzálním kvantifikátorem.
(2)Produkční výraz
Productionexpression,alsoknownasruleexpression,sometimescalledIF-THENexpression,itexpressesacondition-resultform,whichisarelativelysimplewayofexpressingknowledge.ThefollowingpartofIFdescribesTheprerequisiteoftherule,andthefollowingpartofTHENdescribestheconclusionoftherule.Theruleexpressionmethodismainlyusedtodescribeknowledgeandstatethecontrolbetweenvariousprocessknowledge,andthemechanismofinteraction.
Example:TheMYCINsystemhasthefollowingproductionknowledge(whereinconfidenceiscalledrulestrength):
IFThestainofthisorganismisGram-negative,theshapeofthisorganismisrod-shaped,andthepatientisanintermediatehost
THENThemicroorganismisPseudomonasaeruginosa,withaconfidenceof0.6
(3) Rámcová reprezentace
FrameisaspecialeventorobjectAcomplexdatastructureinwhichalloftheknowledgeisstoredtogether.Itsmainbodyisfixed,representingafixedconcept,objectorevent,anditslowerlayeriscomposedofslots,whichrepresenttheattributesofeachaspectofthemainbody.FrameworkItisahierarchicaldatastructure.Theslotinthelowerlayeroftheframecanberegardedasasub-frame,andthesub-frameitselfcanbefurtherdividedintosides.Theattributevaluesoftheslotandthesidearecalledtheslotvalueandthesidevalue,respectively.TheslotvaluecanbeLogicalornumeric,thespecificvaluecanbeaprogram,condition,defaultvalueorasubframe.Interrelatedframesareconnectedtoformaframesystem,orframenetwork.
Example:UseaframeSaidthefollowingearthquakeevents:[VirtualXinhuaNewsAgency,March15th]Yesterday,anearthquakeoccurredinYuxi,Yunnan,causingpropertylossesofabout100,000yuan.Ifthestatisticsdepartmentneedsdetailedlossfigures,pleasecall62332931.AccordingtoexpertsThemagnitudewillnotexceed4,anditisbelievedthatthelocationinnoman’slandwillnotcausecasualties.
(4)Objektově orientovaná metoda reprezentace
Theobject-orientedknowledgerepresentationmethodisAccordingtotheprincipleofobject-orientedprogramming,aformofmixedknowledgerepresentationisformed,thatis,takingtheobjectasthecenter,encapsulatingrelatedknowledgesuchasobjectattributes,dynamicbehavior,domainknowledgeandprocessingmethodsinthestructureofexpressingtheobject.Inthismethod,Thebasicunitofknowledgeisanobject,andeachobjectiscomposedofasetofattributes,relationships,andmethods.Thevalueofanobject’sattributesetandrelationshipsetdescribestheknowledgeoftheobject;themethodsetrelatedtotheobject,Thevalueoftheoperationontheattributesetandtherelationshipsetrepresentstheknowledgeprocessingmethodthattheobjectactsontheknowledge,includingknowledgeacquisitionmethod,reasoningmethod,messagetransmissionmethodandknowledgeupdatemethod.
(5)Sémantická webová reprezentace
SemanticWebisoneofthemostimportantmethodsofknowledgerepresentation.Itisahighlyexpressiveandflexibleknowledgerepresentationmethod.ItAnetworkgraphthatexpressesknowledgethroughconceptsandtheirsemanticrelations.Fromthepointofviewofgraphtheory,itisa"markeddirectedgraph".Thesemanticnetworkusesadirectedgraphcomposedofnodesandlabelededgestodescribetherelationshipbetweenevents,concepts,conditions,actions,andobjects.Thelabeleddirectedgraphcandescribetherelationshipbetweenobjectsverynaturally.
Example:Useasemanticnetworktoexpressthefollowingknowledge:XiangyaMedicalCollegeofCentralSouthUniversityisauniversitylocatedinChangshaCity,andwasestablishedin1914.
(6) Notace založená na XML
InXML(eXtensibleMarkuplanguage,extensiblemarkuplanguage),dataobjectsaredescribedbyelements,andtheattributesofdataobjectscanbedescribedasTheelement'schildelementsorelementattributes.AnXMLdocumentiscomposedofseveralelements,andtherelationshipbetweendataisembodiedinthenestedformofparentelementsandchildelements.IntheprocessofXML-basedknowledgerepresentation,XMLDTD(DocumentTypedefinitions,documenttypedefinitions)isusedtodefineagrammaticalsystemofknowledgerepresentationmethods.InterprettheinstantiatedknowledgerepresentationdocumentthroughacustomXMLapplication.Intheprocessofknowledgeutilization,thecontentmarkedbyaspecifictagisparsedbymaintainingadatadictionaryandanXMLparsingprogram,andthespecificknowledgecontentisexpressedintheformatof"tag"+"content".Knowledgerepresentationisthekeytoconstructingaknowledgebase.Whethertheknowledgerepresentationmethodissuitableornotisnotonlyrelatedtotheeffectivestorageofknowledgeintheknowledgebase,butalsodirectlyaffectstheefficiencyofthesystem'sknowledgereasoningandtheabilitytoacquirenewknowledge.
(7)Ontologická reprezentace
Ontologyisaformal,shared,clear,andconceptualspecification.Ontologycanexpresssemanticsinanexplicitandformalway,improvetheinteroperabilitybetweenheterogeneoussystems,andpromoteknowledgesharing.Therefore,inrecentyears,ontologyhasbeenwidelyusedinthefieldofknowledgerepresentation.Thepurposeofusingontologytoexpressknowledgeistounifytheconceptsintheapplicationdomain,andconstructanontologyhierarchysystemtoexpressthesemanticrelationshipbetweenconcepts,soastorealizethesharingandreuseofknowledgebetweenhumansandcomputers.Fivebasicmodelingprimitivesarethebasiccomponentsoftheontologyhierarchy.Theseprimitivesare:class,relationship,function,axiomandinstance.UsuallyalsoClasses(class)iswrittenasConcepts.Theontologyisintroducedintotheknowledgemodelingoftheknowledgebase,andthedomainontologyknowledgebaseisestablished.Theknowledgecanbeexpressedwithconceptsandtheinherentrelationshipbetweentheseknowledgescanberevealedatthesametime.Theknowledgeinthedomainontologyknowledgebaseisnotonlyclassifiedthroughtheverticalcategory,butalsoorganizedandrelatedthroughthesemanticassociationoftheontology.Theinferenceenginereusesthisknowledgeforreasoning,therebyimprovingtherecallandaccuracyofretrieval.
Theabovebrieflyintroducesandanalyzescommonknowledgerepresentationmethods.Inaddition,therearesomeknowledgerepresentationmethodssuitableforspecialfields,suchas:conceptmap,Petri,grid-basedknowledgerepresentationmethods,roughsets,Theknowledgerepresentationmethodofcloudtheory,etc.,willnotbeintroducedindetailhere.Intheactualapplicationprocess,anintelligentsystemoftencontainsmultiplerepresentationmethods.
Kompletní proces
Inageneralsense,knowledgerepresentationisasetofconventionsfordescribingtheworld,whichisthesymbolization,formalizationormodelingofknowledge;fromcomputerscienceFromthepointofview,knowledgerepresentationisageneralmethodtostudythefeasibilityandeffectivenessofcomputerrepresentationofknowledge.Itisastrategytorepresenthumanknowledgeasadatastructureandsystemcontrolstructurethatcanbeprocessedbyamachine.
Acompleteknowledgerepresentationprocessis:first,thedesignerdesignsavarietyofknowledgerepresentationmethodsforvarioustypesofproblems;thentheuseroftherepresentationmethodselectsasuitablerepresentationmethodtorepresentacertaintypeofknowledge;finallytheknowledgeTheuserusesorlearnstheknowledgeprocessedbytherepresentationmethod.Therefore,theobjectofknowledgerepresentationisknowledge;thesubjectofknowledgerepresentationincludesthreecategories:designersofrepresentationmethods,usersofrepresentationmethods,andusersofknowledge.Specifically,thesubjectofknowledgerepresentationmainlyreferstopeople(individualsorcollectives),andsometimescomputers.
TheprocessofknowledgerepresentationisshowninFigure1."KnowledgeI"inFigure1referstotacitknowledgeorexplicitknowledgeexpressedusingotherrepresentationmethods;"KnowledgeII"referstoexplicitknowledgeexpressedusingthisknowledgerepresentationmethod.Thedeepstructureof"KnowledgeI"and"KnowledgeII"arethesame,buttherepresentationisdifferent.Therefore,theprocessofknowledgerepresentationistheprocessoftransformingtacitknowledgeintoexplicitknowledge,ortheprocessoftransformingknowledgefromoneformofrepresentationintoanother.
Související příklady
Supposethereissuchaknowledgethatneedstobeexpressed:XiaoPanisastudentintheDepartmentofComputerScience,buthedoesnotlikeprogramming.Ifweusefirst-orderpredicatelogictoexpressit,weneedtotakethefollowingsteps:First,definethepredicate
Počítač(x):x je student katedry počítačových věd
Like(x,y):xlikesy
Za druhé, je vyjádřeno predikátovým vzorcem:
Počítač (xiaopan)∧¬Like (xiaopan, programování)
Productionrules:Amethodofexpressingknowledgeusedinthejudgmentofconditions,causationandothertypes.ThebasicformisP→Q,orifPthenQ.Herethisproductionruleisdifferentfromtheexpressionof"implication(→)"inthepredicatelogicjustnow.Thelatterisanexactmatch,thatis,ifx,100%willbey,whiletheformercanbeRepresentsafuzzymatchwithacertaindegreeofconfidence,thatis,theprobabilityofoccurrence.
Forexample:if"coughandfever",then"cold",theconfidencelevelis80%.Heretheifpartindicatestheconditionpart,thethenpartindicatestheconclusionpart,andtheconfidencedegreeindicatestheprobabilityofobtainingaconclusionwhentheconditionismet.Thiswholepartformsarulethatexpressesthiskindofcausalknowledge:"Ifthepatienthasafeverandcough,thenheislikelytohaveacold."
Therefore,formorecomplexsituations,wecanusethisknowledgerepresentationofproductionrulestoformaseriesofrules.