Expert Systems - Computer Science Department - Montana State 专家系统-计算机科学系,蒙大纳州-PPT精品ppt课件.ppt

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1、ExpertSystemsandTheirApplicationsJohnPaxtonMontanaStateUniversityAugust14,2019BozemanDefinitionsAmodelandassociatedprocedurethatexhibits,withinaspecificdomain,adegreeofexpertiseinproblemsolvingthatiscomparabletothatofahumanexpert.(Ignizio)Anexpertsystemisacomputersystemwhich

2、emulatesthedecision-makingabilityofahumanexpert.(Giarratono)CharacteristicsOperatesinanarrowdomainSeparatesknowledgefromprocessingCanexplainhowaparticularconclusionisreachedCanexplainwhyspecificdataisneededPermitsinexactreasoningCanmakemistakesChangesareeasytoincorporateComp

3、onentsProgram=Algorithm+DataStructureExpertSystem=InferenceEngine+KnowledgeUsage(2019)AreaPercentageProduction/OpsMgmt48%Finance17%InformationSystems12%Marketing/Transactions10%Accounting/Auditing6%InternationalBusiness3%HumanResources2%Other2%WhyUseanExpertSystem?Helpsprese

4、rveknowledge--buildsupthecorporatememoryofthefirm.Helpsifexpertiseisscarce,expensive,orunavailable.Helpsifundertimeandpressureconstraints.Helpsintrainingnewemployees.Helpsimproveworkerproductivity.ArchitectureUSERINTERFACEKNOWLEDGEBASEINFERENCEENGINEWORKINGMEMORYKnowledgeB

5、aseContainsfactsantacid(Imodium)Containsrulesiftraveler(x)andstomach-pains(x)thentake(y,antacid(y))InferenceEngineRulesthatmatchworkingmemoryareidentifiedandthenfired.Thisupdatesworkingmemoryandtheknowledgebase.Theprocessisrepeated.InferenceEngineConflictResolutionfireallma

6、tchingrulesfirethefirstmatchingrulefirethehighestprioritymatchingrulefirethemostspecificrulefiretherulethatusesthemostrecentdataInferenceEngineForwardChaining.Startingwiththedata,aconclusionisreached.cat(Mulder)cat(x)mammal(x)BackwardChaining.Startingwithahypothesis,itwo

7、rksbackwardstothedata.UncertaintySourcesWeakimplicationsImpreciselanguage(e.g.“often”)UnknowndataCombiningviewsofdifferentexpertsUncertaintyCertaintyFactors.Dempster-ShaferTheory.BayesianNetworks.FuzzyLogic.CertaintyFactorsIFthelightisgreenTHENitisoktocrossthestreetcf=0.9+

8、easytocompute+easytopropagate-somewhatadhoc-allcertaintyfactorsareindepende