架构质量属性

11AddressingQualityRequirementsinGISArchitecturesIbrahimHabliGISServicesDivisionKhatib&Alami(CEC)LebanonTimKellyDepartmentofComputerScienceUniversityofYorkUnitedKingdomTS14.1SIMandQualityFromPharaohstoGeoinformatics,FIGWorkingWeek2005andGSDI-8,Cairo,EgyptApril16-21,20052HighQualityGISAttentionisoftenpaidtoGISfunctionalitiesHowever,qualityaspectsareinsufficientlyaddressed.AGISwouldbe:IneffectiveIneffectiveifitsprocessingmissesdeadlinesUnreliableUnreliableifitisnotavailablewhenitshouldbeUnusableUnusableifitisdifficulttounderstandHence,highqualityGISsystemsdependonqualities,suchasEfficiencyReliabilityUsabilitySecurity3ProblemswithGISQualityRequirementsComplexityandlargevolumeofgeographicinformationOftennotsystematicallycaptured&documentedCommontofindambiguousstatementssuchas:““SystemshallbeportableSystemshallbeportable””““SystemshallbehighlysecuredSystemshallbehighlysecured””““GISoperationsshallbeefficientGISoperationsshallbeefficient””Hence,nofeasiblemeanstoassesswhetherthesystemhasmetitsqualityrequirementsornot4Solution:ArchitecturalFrameworkBasedontwoarchitecturaltechniquesfromtheSSoftwareEEngineeringIInstitute(SEI):(SEI):QualityAttributeScenariosAttributeDrivenDesignMethod(ADD)QualityAttributeScenarios&UseCasesConceptualArchitecture5QualityAttributeScenariosSEIqualityattributescenariosconsistof6yardsticks:1.Sourceofstimulus2.Stimulus3.Environment4.Artifact5.Response6.ResponsemeasureSource:GISadministratorStimulus:TheadministratorrequeststoconvertthedataformatofaportionoftheGISdataArtefact:GISsystem(Datasource)Environment:RuntimeResponse:TherequiredformatisconvertedwithnodatainconsistencyResponseMeasure:Numberofelementsaffected/programmingeffort/dataloss6AttributeDrivenDesignMethodAttributeDrivenDesignMethod(ADD)isarecursiveapproachtosoftwarearchitecturedesignbasedonthequalityattributesthesoftwareneedstoachieve1.Chooseonedesignelement2.Choosethearchitecturaldriversi.e.qualityrequirements3.Choosearchitecturalpatterns4.Assignfunctionalitytoeachofthedesignelements(resultingfromthedecomposition)5.VerifythatthedecompositionhasaddressedtheselectedarchitecturaldriversQualityAttributeScenarios&UseCasesConceptualArchitecture27AchievingGISQualityRequirementsusingADDQualityrequirementscenariosaddressed:PerformanceEditingaGeographicFeatureRetrieveDataModifiabilityChangeGISDataFormatAddGISComponentInterfaceGISwithanExternalSoftwareSystem8FirstLevelofDecompositionSystemGISSubsystemUser-InterfaceSubsystemApplicationsSubsystemDataSubsystemOperatingSystemSubsystemCommunication•Scenariosaddressedatthisstage:AddGISComponentChangeGISDataFormatEditingaGeographicFeatureRetrieveDataArchitecturalDecisions:MaintainsemanticcoherencePublishedinterfacesClient-ServerMinimizeclients&serversinteraction9SecondLevelofDecomposition:ApplicationsSubsystemDecompositionScenariosaddressedatthisstage:MediatordesignpatternUsegeographicinformationstandardsSeparationunitoperationArchitecturalDecisions:InterfaceGISwithanExternalSoftwareSystemChangeGISDataFormatEditingaGeographicFeatureRetrieveDataSubsystemUser-InterfaceSubsystemApplicationsSubsystemDataSubsystemOperatingSystemSubsystemCommunication10QualityAttributeScenarios:EditingaGeographicFeatureRetrieveDataChangeGISDataFormatAddGISComponentInterfaceGISwithanExternalSoftwareSystemSubsystemDataFacadeSubsystemAttributeDataSubsystemGeographicDataSubsystemFileBasedDataIGeographicDataIAttributeDataIFileBasedDataIDataFacadeSubsystemDataSecurityIDataSecuritySubsystemApplicationSecuritySubsystemServicesSubsystemMediatorSubsystemReal-TimeServicesIServicesIApplicationSecurityIMediatorIReal-TimeServicesSubsystemApplicationFacadeIApplicationFacadeSubsystemGUIIGUISubsystemThickGUIIThickGUISubsystemThinGUIIThinGUISubsystemExternalInterfaceIExternalInterfaceSubsystemSWInterfaceISWInterfaceSubsystemHWInterfaceIHWInterfaceSubsystemUIAdapterIUIAdapterUser-InterfaceSubsystemDataSubsystemApplicationsSubsystemArchitecturalDecisions:1.Maintainsemanticcoherence2.Publishedinterfaces3.Client-Serverstyle4.Minimizeclients&serversinteraction5.Dataaccessordesignpattern6.Façadedesignpattern7.Concurrency8.Caching9.Increasehardwareresources10.Mediatordesignpattern11.Geographicinformationstandards12.Separationunitoperation13.Generalizationstyle14.Adapter(orwrapper)design11Evaluation:GISQualityAttributeScenariosUnderstandability:scenariosunambiguouslydefinefactorscontrollingtheachievementofqualityattributesPrecision:responseandresponsemeasureofferspecificmeansforassessingGISarchitecturesTraceability:decomposingeachqualityattributeintoscenariosenablestraceabilityofhowanattributeisaddressedduringthearchitecturaldesignandevaluation12Evaluation:GISArchitectureDesignAttributeDrivenDesignMethod:SimplifiesarchitecturaldesignprocessSystematicconsiderationofqualityattributesMappingbetweenqualityattributescenarios&architecturaldecisionsDesignDocumentation:Wellorganizedarchitectu