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1、TheEntity-RelationshipModel-TowardaUnifiedViewofDataPETERPIN-SHANCHENMassachusettsInstituteofTechnologyAdatamodel,calledtheentity-relationshipmodel,isproposed.Thismodelincorporatessomeoftheimportantsemanticinformationabouttherealworld.Aspecialdiagrammatictech
2、niqueisintroducedasatoolfordatabasedesign.Anexampleofdatabasedesignanddescriptionusingthemodelandthediagrammatictechniqueisgiven.Someimplicationsfordataintegrity,infor-mationretrieval,anddatamanipulationarediscussed.Theentity-relationshipmodelcanbeusedasabasi
3、sforunificationofdifferentviewsofdata:t,henetworkmodel,therelationalmodel,andtheentitysetmodel.Semanticambiguitiesinthesemodelsareanalyzed.Possiblewaystoderivetheirviewsofdatafromtheentity-relationshipmodelarepresented.KeyWordsandPhrases:databasedesign,logica
4、lviewofdata,semanticsofdata,datamodels,entity-relationshipmodel,relationalmodel,DataBaseTaskGroup,networkmodel,entitysetmodel,datadefinitionandmanipulation,dataintegrityandconsistencyCRCategories:3.50,3.70,4.33,4.341.INTRODUCTIONThelogicalviewofdatahasbeenani
5、mportantissueinrecentyears.Threemajordatamodelshavebeenproposed:thenetworkmodel[2,3,71,therelationalmodel[S),andtheentitysetmodel[25].Thesemodelshavetheirownstrengthsandweaknesses.Thenetworkmodelprovidesamorenaturalviewofdatabyseparatingentitiesandrelationshi
6、ps(toacertainextent),butitscapabilitytoachievedataindependencehasbeenchallenged[S].Therelationalmodelisbasedonrelationaltheoryandcanachieveahighdegreeofdataindependence,butitmaylosesomeimportantsemanticinformationabouttherealworld[12,15,231.Theentitysetmodel,
7、whichisbasedonsettheory,alsoachievesahighdegreeofdatainde-pendence,butitsviewingofvaluessuchas“3”or“red”maynotbenaturaltosomepeople[25].Thispaperpresentstheentity-relationshipmodel,whichhasmostofthead-vantagesoftheabovethreemodels.Theentity-relationshipmodela
8、doptsthemorenaturalviewthattherealworldconsistsofentitiesandrelationships.ItCopyright@1976,AssociationforComputingMachinery,Inc.Generalpermissiontorepublish,butnotforprofit;allorpartofthi
