数据库 chp1_1264_lecture_5_F2002_data_model

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1、1.264Lecture5Datamodeling1.Datamodels•Datamodelisrepresentationof–Things(orentitiesorobjects)ofimportancetoabusiness–Howthethingsrelatetoeachother•Itisbuiltandmodifieduntilitrepresentsthebusinesswellenoughtowriteasystem.•Dataflow,statemodels,andothersinUnifiedModelingLanguage[UML]arealsoused•

2、Datamodelsaresometimesbuiltduringrequirements,andothertimesduringdesignphaseLogicaldatamodeling•Methodtodiscoverthedata,relationshipsandrulesofabusiness,collectivelycalledthebusinessrules•Logicaldatamodelsarethebasisof:–Physicaldatamodels,oractualdatabases–Applications,partsofwhichcanbeautoma

3、ticallygeneratedfromthedatamodel•SmallmodelforEZBrokeroftransportationservices–Small,butsaysalotaboutEZBroker–Givesgoodpictureofwhatdatabaseshouldlooklike–Alsogivesgoodpictureofunderlyingbusinessrulesofbroker•Usefulinrequirementsanalysisandscrubbing!EZBrokerDataModelCommoditytypeCarrierBroker

4、(company)CommTypeCodeCarrierNbrrepresentsBrokerNbrCommTypeDescCarrierNameBrokerNameChemicalAgriculaturalAutomotivecarriesissuesemploysContractCustomerContractNbrAgentAgentNbrCustomerNbrservedbyCarrierNbrsellsAgentNbrCustomerNameCustomerNbrAgentNameContractDateBrokerNbrCommTypeCodeassociatedwi

5、thRefrigeratedEquipmenttypeTank/liquidEquipmentTypeOversizeEquipmentTypeDescEZBrokerBusinessRules•Acarriercanbeassociatedwithmanybrokers•Abrokercanbeassociatedwithmanycarriers•Acarriercanissuemanycontracts•Acontractisissuedbyonecarrier•Abrokercanemploymanyagents•Anagentisemployedbyonebroker•A

6、nagentcansellmanycontracts•Acontractisservicedbyonlyoneagent•Acontractcanservetocarryonlyonecommoditytype•Acommoditytypecanbecarriedundermanycontracts•Acontractcanbeassociatedwithmanyequipmenttypes•Anequipmenttypecanbeassociatedwithmanycontracts•Acustomercanbeservedbymanycontracts•Acontractco

7、versonecustomerDatamodelpurpose•Businessneedstobuildlogicaldatamodelsousersanddevelopersbothunderstandbusinessrulesofcompany–Modelsenableusersanddeveloperstohavesingleviewofsystem–Sometimesusersnotethisisfirsttimetheyunderstoodbusinessrules!–