系统分析与设计方法-第七版-影印版.ppt

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1、DataMODELINGANDAnalysisWhatIsDataModeling?Datamodelingisatechniquefororganizinganddocumentingasystem'sdata.Datamodelingissometimescalleddatabasemodelingbecauseadatamodelisusuallyimplementedasadatabase.SystemConceptsForDataModeling>Entitiesaclassofpersons,places,objects,events,orconceptsabo

2、utwhichweneedtocaptureandstoredata.>Attributesadescriptivepropertyorcharacteristicofanentity.Synonymsincludeelement,property,andfield.>Relationshipsanaturalbusinessassociationbetweenoneoneormoreentities.Relationships￭>nonidentifyingrelationshiarelationshipinwhicheachparticipatingentityhasi

3、tsowmindependentprimarykey.￭>identifyingrelationshiparelationshipinwhichtheparententity'skeyisalsopartoftheprimarykeyofthechildentity.￭>nonspecificrelationshiparelationshipwheremanyinstancesofanentityareassociatedwithmanyinstancesofanotherentity.Alsocalledmany-to-manyrelationship.TheProces

4、sOfLogicalDataModelingStrategicDataModelingDataModelingduringSystemsAnalysisLookingAheadtoSystemsDesignAutomatedToolsforDataModelingHowtoConstructDataModelsEntityDiscoveryTheContextDataModelTheKey-BasedDataModelGeneralizedHierarchiesTheFullyAttributedDataModelAnalyzingtheDataModel￭WhatisaG

5、oodDataModel?1.Agooddatamodelissimple.2.Agooddatamodelisessentiallynonredundant.3.Agooddatamodelshouldbeflexibleandadaptabletofutureneeds.￭DataAnalysisatechniqueusedtoimproveadatamodelforimplementationasadatabase.￭NormalizationExampleadataanalysistechniquethatorganizesdataintogroupstoformn

6、onredundant,stable,flexible,andadaptiveentities.Normalization￭firstnormalform(1NF)anentitywhoseattributeshavenomorethanonevalueforasingleinstanceofthatentity.￭secondnormalform(2NF)anentitywhosenon-primary-keyattributesaredependentonthefullprimarykey.￭thirdnormalform(3NF)anentitywhosenon-pr

7、imary-keyattributesarenotdependentonanyothernon-primary-keyattributes.MappingDataRequirementstoLocationsdata-to-location-CRUDmatrixamatrixthatisusedtomapdatarequirementstolocations.