0b304软件需求工程-lecture

Lecture6:RequirementsYanTheSchoolofSoftwareandPeKing6-LectureLecture

IntroductiontosoftwareRequirements 14-09-GoodPracticesforRequirements 14-09-LectureLectureLectureLectureLectureLectureLecture

RequirementsElicitation RequirementsSpecificationProjectandDiscussion(1)RequirementsValidationRequirementsManagement

14-09-14-10-14-10-14-10-14-11-14-11-14-11-Lecture10:ProjectandLecture11:PracticesandLecture12:

14-11-14-12-14-12-6-BusinessRules:WhatandTheSoftwareRequirementsSpecification:ATemplateTheDataSoftwareQuality6-PlayingbytheASimpleBusinessRuleBusinessRulesandTheSoftwareRequirementsASoftwareRequirementsSpecificationTheDataSoftwareQualityAttributesImportanttoAttributesImportantto6-PlayingbytheEverybusinessorganizationoperatesaccordingtoanextensivesetofcorporatepolicies,laws,andindustrystandards.Suchcontrollingprinciplesarecollectivelyknownasbusinessrules.6-PlayingbytheRulesBusinessrulesareamajorsourceofsoftwarefunctionalrequirementsbecausetheydictatecapabilitiesthatthesystemmustpossesstoconformtotherules. edbusinessrulesknownonlytoexpertsresultinaknowledgevacuumwhenthoseexpertsretireorchangejobs.6-TheRulesoftheAccordingtotheBusinessRulesGroup"Abusinessruleisastatementthatdefinesorconstrainssomeaspectofthebusiness.Itisintendedtoassertbusinessstructureortocontrolorinfluencethebehaviorofthe6-PlayingbytheASimpleBusinessRuleBusinessRulesandTheSoftwareRequirementsASoftwareRequirementsSpecificationTheDataSoftwareQualityAttributesImportanttoAttributesImportantto6-ASimpleBusinessRule6-ASimpleBusinessRuleTaxonomyThesimpleschemeshownwithfivetypesofbusinessruleswillworkformostAsixthcategoryisterms,definedwords,phrases,andabbreviationsthatareimportanttothebusiness.Aglossaryisaconvenientplacetodefine6-Factsaresimplystatementsthataretrueaboutthebusiness.OftenfactsdescribeassociationsorrelationshipsbetweenimportantbusinessFactsarealsocalledinvariants—immutabletruthsaboutdataentitiesandtheirattributes.6-FactsExamplesoffactsEverychemicalcontainerhasauniquebarcodeEveryordermusthavea Eachlineiteminanorderrepresentsaspecificcombinationofchemical,grade,containersize,andnumberofcontainers.NonrefundableticketsincurafeewhenthechangestheSalestaxisnotcomputedon 6-Constraintsrestricttheactionsthatthesystemoritsusersmayperform.Somewordsandphrasesthatsuggestsomeoneisdescribingaconstraintbusinessrulearemust,mustnot,maynot,andonly.6-ConstraintsExamplesofconstraintsAborrowerwhoislessthan18yearsoldmusthaveaparentalegalguardianascosignerontheAlibrarypatronmayplaceupto10itemsonAusermayrequestachemicalontheLevel1hazardlistonlyifhehashadhazardous-chemicaltrainingwithinthepast12Allsoftwareapplicationsmustcomplywith regulationsforusagebyvisuallyimpaired Correspondencemaynotdisplaymorethanfourdigitsofthepolicyholder'sSocialSecuritynumber.Commercialairlineflightcrewsmustreceiveatleasteightofcontinuousrestinevery24-hour6-ConstraintsManybusinessrulesimposeconstraintsonthewaythebusinessoperates.Whenevertheseconstraintsarereflectedinthesoftwarefunctionalrequirements,indicatethepertinentruleastherationaleforeachsuchderivedrequirement./6-ActionArulethattriggerssomeactivityunderspecificconditionsisanactionenabler.Astatementintheform"If<someconditionistrueorsomeeventtakesplace>,then<somethinghappens>"isacluethatsomeoneisdescribinganaction6-ActionEnablersFollowingaresomeexamplesofaction-enablingbusinessrules:Ifthechemicalstockroomhascontainersofachemicalinstock,thenofferexistingcontainerstotheIftheexpirationdateforachemicalcontainerhasbeenthennotify whocurrentlypossessesthatOnthelastdayofacalendarquarter,generatethemandatedOSHA(OccupationalSafetyandHealthAct[Administration])andEPA(EnvironmentalProtectionAgency)reportsonchemicalhandlinganddisposalforthatquarter.Ifthecustomerorderedabookbyanauthorwhohaswrittenmultiplebooks,thenoffertheauthor'sotherbookstothecustomerbeforeacceptingtheorder./6-Sometimescalledinferredknowledge,aninferenceisarulethatestablishessomenewknowledgebasedonthetruthofcertainconditions.Aninferencecreatesanewfactfromotherfactsorfromcomputations.Inferencesareoftenwritteninthe"if/then"6-InferencesSomeexamplesofinferencesIfapaymentisnotreceivedwithin30calendardaysofthedateitisdue,thentheaccountisdelinquent.Ifthevendorcannotshipanordereditemwithinfivedaysofreceivingtheorder,thentheitemisback-AcontainerofachemicalthatcanformexplosivepositionproductsisconsideredexpiredoneyearafteritsmanufactureChemicalswithanLD50toxicitylowerthan5mg/kginmiceareconsideredhazardous./6-Oneclassofbusinessrulesdefinescomputationsthatareperformedusingspecificmathematicalformulasor6-ComputationsFollowingaresomeexamplesofcomputationalbusinessrulesintextformTheunitpriceisreducedby10%forordersof6to10units,by20%ordersof11to20units,andby35%forordersofmorethan20Thedomesticground chargeforanorderthatweighsthan2poundsis$4.75plus12centsperounceoffractionThecommissionforsecuritiestradescompletedonlineis$12pertradeof1through5000shares.Thecommissionfortradesconductedthroughanaccountofficeris$45pertradeof1through5000shares.Commissionsontradesofgreaterthan5000sharesareone-halfofthesecommissions.Thetotalpriceforanorderiscomputedasthesumofthepriceoftheitemsordered,lessanyvolumediscounts,plusstateandcountysalestaxforthelocationtowhichtheorderisbeingshipped,plustheshipcharge,plusanoptionalinsurancecharge.6-ComputationsTable9-1:UsingaTabletoRepresentComputationalBusinessNumberofUnits1through06through11throughmorethan6-ingBusinessBecausebusinessrulescaninfluencemultipleapplications,organizationsshouldmanagetheirbusinessrulesasenterprise-level—notproject-level—assets.Applystructuredtemplatesfordefiningrulesofdifferenttypes.6-PlayingbytheASimpleBusinessRuleBusinessRulesandTheSoftwareRequirementsASoftwareRequirementsSpecificationTheDataSoftwareQualityAttributesImportanttoAttributesImportantto6-BusinessRulesandDependingontheapplication,sometimesyouinventbusinessrulesasyougoalongandsometimesyoudiscoverthemduringrequirementsdiscussions.Duringuserrequirementselicitationworkshops, ystcanaskquestionstoprobearoundtherationalefortherequirementsandconstraintsthatuserspresent.Thesediscussionsfrequentlysurfacebusinessrulesastheunderlyingrationale.6-Discoveringbusinessrulesbyaskingquestionsfrom 6-BusinessRulesandRequirementsAfteridentifyingand businessrules,determinewhichonesmustbeimplementedintheSomeruleswillleadtousecasesandhencetofunctionalrequirementsthatenforcetherule.6-BusinessRulesandRequirementsConsiderthefollowingthreeRule#1(actionenabler)"Iftheexpirationdateforachemicalcontainerhasbeenreached,thennotifythewhocurrentlypossessesthatRule#2(inference)"Acontainerofachemicalthatcanformexplosive positionproductsisconsideredexpiredoneyearafteritsmanufactureRule#3(fact)"Etherscanspontaneouslyformexplosiveperoxides."6-BusinessRulesandRequirementsTheserulesserveastheoriginforausecasecalled"NotifyChemicalOwnerofUseBusinessOnefunctionalrequirementforthatUseBusiness6-BusinessRulesandRequirementsYoucandefinethelinksbetweenafunctionalrequirementanditsparentbusinessrulesinthefollowingtwoways:Usearequirementattributecalled"Origin"andindicatetherulesastheoriginofthefunctionalrequirement.Definetraceabilitylinksbetweenafunctionalrequirementandthepertinentbusinessrulesintherequirementstraceabilitymatrix.6-BusinessRulesandRequirementsDatareferentialintegrityrulesfrequentlyareimplementedintheformofdatabasetriggersorstoredprocedures.Suchrulesdescribethedataupdates,insertions,anddeletionsthatthesystemmustperformbecauseofrelationshipsbetweendataentities(vonHalle2002).Forexample,thesystemmustdeleteallundeliveredlineitemsinanorderifthecustomercancelstheorder.6-BusinessRulesandRequirements ystmustdecidewhichexistingrulespertaintohisapplication,whichonesmustbeenforcedinthesoftware,andhowtoenforcethem.6-BusinessRulesandRequirementsTopreventredundancy,don'tduplicaterulesfromyourbusinessrulescatalogintheSRS.Instead,theSRSshouldreferbacktospecificrulesasthesourceofalgorithms.6-BusinessRulesandRequirementsThisapproachprovidesseveralItobviatestheneedtochangeboththebusinessruleandthecorrespondingfunctionalrequirementsiftherulechanges.ItkeepstheSRScurrentwithrulechangesbecausetheSRSsimplyreferstothemastercopyoftherule.ItfacilitatesreusingthesameruleinseveralplacesintheSRSandacrossmultipleprojectswithoutriskinganinconsistency,becausetherulesarenotburiedin ationforanysingleapplication./6-课堂讨6-WhatandThevisionandscope thebusinessrequirements,andtheuserrequirementsoftenarecapturedintheformofusecases.Theproduct'sdetailedfunctionalandnonfunctionalrequirementsresideinasoftwarerequirementsspecification(SRS).6-WhatandWhere?Wecanrepresentsoftwarerequirementsinseveralways: sthatusewell-structuredandcarefullywrittennaturallanguageGraphicalmodelsthatillustratetransformationalprocesses,systemstatesandchangesbetweenthem,datarelationships,logicflows,orobjectclassesandtheirrelationshipsFormalspecificationsthatdefinerequirementsmathematicallypreciseformallogic6-RUP 6-WhatandWhere?Eventhefinestrequirementsspecificationcanneverreplaceinter aldiscussionsthroughouttheproject.It'simpossibletodiscovereveryfragmentofinformationthatfeedsintosoftwaredevelopmentupfront.Keepthecommunicationlinesopenbetweenthedevelopmentteam,customerrepresentatives,testers,andotherstakeholderssothattheycanquicklyaddressthemyriadissuesthatwillarise.6-PlayingbytheASimpleBusinessRuleBusinessRulesandTheSoftwareRequirementsASoftwareRequirementsSpecificationTheDataSoftwareQualityAttributesImportanttoAttributesImportantto6-TheSoftwareRequirementsTheSRSpreciselystatesthefunctionsandcapabilitiesthatasoftwaresystemmustprovideandtheconstraintsthatitmustrespect.TheSRSisthebasisforallsubsequentprojectplanning,design,andcoding,aswellasthefoundationforsystemtestinganduser 6-TheSoftwareRequirementsSpecification(cont’d)SeveralaudiencesrelyontheCustomers,themarketingdepartment,andsalesstaffneedtoknowwhatproducttheycanexpecttobeProjectmanagersbasetheirestimatesofschedule,effort,andresourcesontheproductdescription.TheSRS lsthesoftwaredevelopmentteamwhattoThetestinggroupusestheSRStodeveloptestplans,testcases,andprocedures.TheSRS lsmaintenanceandsupportstaffwhateachpartoftheproductissupposedtodo.6-TheSoftwareRequirementsSpecification(cont’d)SeveralaudiencesrelyontheSRS ationwritersbaseusermanualsandhelpscreensontheSRSandtheuserinterfacedesign. nelusetheSRSandationtodevelopeducationalLegalstaffensurethattherequirementscomplyapplicablelawsandSubcontractorsbasetheirworkon,andcanbeheldto,the6-TheSoftwareRequirementsSpecification(cont’d)Astheultimaterepositoryfortheproductrequirements,theSRSmustbeYoudon'thavetowritetheSRSfortheentireproductbeforebeginningdevelopment,butyoudoneedtocapturetherequirementsforeachincrementbeforebuildingthatincrement.6-TheSoftwareRequirementsSpecification(cont’d)BaseliningistheprocessoftransitioninganSRSunderdevelopmentintoonethathasbeenreviewedandapproved.6-TheSoftwareRequirementsSpecification(cont’d)Keepthefollowingrequirementsreadabilitysuggestionsinmind:Labelsections,subsections,andindividualrequirementsconsistently.Leavetextraggedontherightmargin,ratherthanfullyjustified.Usewhitespaceliberally,Usevisualemphasis(suchasbold,underline,italics,anddifferentfonts)consistentlyandjudiciously.Createatableofcontentsandperhapsanindextohelpreadersfindtheinformationtheyneed.6-TheSoftwareRequirementsSpecification(cont’d)Keepthefollowingrequirementsreadabilitysuggestionsinmind(cont’d):Numberallfiguresandtables,givethemcaptions,andrefertothembynumber.Useyourwordprocessor'scross-referencefacilityratherthanhard-codedpageorsectionnumberstorefertootherlocationswithina UsehyperlinkstoletthereaderjumptorelatedsectionsintheSRSorinother Useanappropriatetemplatetoorganizeallthenecessaryinformation./6-LabelingTosatisfythequalitycriteriaoftraceabilityandmodifiability,everyfunctionalrequirementmustbeuniquelyandpersistentlyidentified.SequenceHierarchicalTextual6-Dealing Sometimesyouknowthatyoulackapieceofinformationaboutaspecificrequirement.Youmightneedtoconsultwithacustomer,checkanexternalinterfacedescription,orbuildaprototypebeforeyoucanresolvethisUsethenotationTBD(tobedetermined)toflagtheseknowledgegaps.ResolveallTBDsbeforeimplementingasetofrequirements.6-UserInterfacesandtheIncorporatinguserinterfacedesignsintheSRShasbothdrawbacksandbenefits.6-UserInterfacesandtheSRSOntheminusscreenimagesanduserinterfacearchitecturesdescribesolutions(designs),notrequirements.

Ontheplusexploringpossibleuserinterfaces(suchaswithaworkingprototype)makestherequirementstangibletobothusersand6-UserInterfacesandtheSRSAsensiblebalanceistoincludeconceptualimages—sketches—ofselecteddisplaysintheSRSwithoutdemandingthattheimplementationpreciselyfollowthosemodels./6-PlayingbytheASimpleBusinessRuleBusinessRulesandTheSoftwareRequirementsASoftwareRequirementsSpecificationTheDataSoftwareQualityAttributesImportanttoAttributesImportantto6-6-RUP版需求规文档概目背定义、首字母缩写词和缩略参考资概整体说用例模假设与依赖关具体需用例描补充需求[易用性、可靠性、性支持信Volere版需求规PartI：项目驱、项目的目、客户、顾客和其他风险其他风险承担、产品的用用户和服务技术人PartII：产品限制条、强制的限制条、命名惯例和定假

PartIII：功能性需、工作的范当前的状工作的上下文范工作切、产品的范产品边产品用单个产品用、功能性需求与数据需功能性需PartIV：非功能需求10、观感需求风格需、易用性和人性化需易于使用的需 、执行需速度和延迟需可靠性和 性需可伸缩性和可扩展需需ASoftwareRequirementsSpecificationTemplateManypeopleusetemplatesderivedfromtheonedescribedinIEEEStandard830-1998, mendedPracticeforSoftwareRequirementsSpecifications"(IEEE1998b).Ifyourorganizationtacklesvariouskindsorsizesofprojects,suchasnew,largesystemdevelopmentaswellasminorenhancementstolegacysystems,adoptanSRStemplateforeachmajorprojectclass.6-anSRStemplatethatwasadaptedfromtheIEEE830standardIfasectionofyourtemplatedoesn'tapplytoaparticularproject,leavethesectionheadinginplacebutindicatethatitisn'tapplicable.Thiswillkeepthereaderfromwonderingwhethersomethingimportantwasomittedinadvertently.Ifyourprojectsconsistentlyomitthesamesections,it'stimetotuneupthetemplate.6-1.TheintroductionpresentsanoverviewtohelpthereaderunderstandhowtheSRSisorganizedandhowtouseit.6-1.Introduction1.1Identifytheproductorapplicationwhoserequirementsarespecifiedinthis includingtherevisionorreleasenumber.IfthisSRSpertainstoonlypartofanentiresystem,identifythatportionorsubsystem.6-1.Introduction Describeanystandardsortypographicalconventions,includingtextstyles,highlighting,orsignificantnotations.6-1.Introduction1.3IntendedAudienceandReadingListthedifferentreaderstowhomtheSRSisDescribewhattherestoftheSRScontainsandhowitisorganized.Suggestasequenceforreadingthatismostappropriateforeachtypeofreader.6-Introduction1.4ProjectProvideashortdescriptionofthesoftwarebeingspecifiedanditspurpose.Relatethesoftwaretouserorcorporategoalsandtobusinessobjectivesandstrategies.6-Introduction1.5Listany sorotherresourcestowhichthisSRSrefers,includinghyperlinkstothemifpossible./6-OverallThissectionpresentsahigh-leveloverviewoftheproductandtheenvironmentinwhichitwillbeused,theanticipatedproductusers,andknownconstraints,assumptions,and6-OverallDescription2.1Describetheproduct'scontextand2.2ProductListthemajorfeaturestheproductcontainsorthesignificantfunctionsthatitperforms.2.3UserClassesandIdentifythevarioususerclassesthatyouanticipatewillusethisproductanddescribetheirpertinentcharacteristics.6-2.OverallDescription2.4OperatingDescribetheenvironmentinwhichthesoftwarewilloperate,includingthehardwareplatform,theoperatingsystemsandversions,andthegeographicallocationsofusers,servers,anddatabases.6-2.OverallDescription2.5DesignandImplementationDescribeanyfactorsthatwillrestricttheoptionsavailabletothedevelopersandtherationaleforeachconstraint.6-2.OverallDescription2.5DesignandImplementationConstraints(cont’d)ConstraintsmightincludetheSpecifictechnologies,tools,programminglanguages,anddatabasesthatmustbeusedorRestrictionsbecauseoftheproduct'soperatingenvironment,suchasthetypesandversionsofWebbrowsersthatwillbeused.6-2.OverallDescription2.5DesignandImplementationConstraints(cont’d)ConstraintsmightincludetheRequireddevelopmentconventionsorstandards.(Forinstance,ifthecustomer'sorganizationwillbemaintainingthesoftware,theorganizationmightspecifydesignnotationsandcodingstandardsthatasubcontractormustfollow.)BackwardcompatibilitywithearlierLimitationsimposedbybusinessrules(whichareedelsewhere).6-2.OverallDescription2.5DesignandImplementationConstraints(cont’d)ConstraintsmightincludetheHardwarelimitationssuchastimingrequirements,memoryorprocessorrestrictions,size,weight,materials,orcost.Existinguserinterfaceconventionstobefollowedwhenenhancinganexistingproduct.Standarddatainterchangeformatssuchas6-OverallDescription2.6 Listtheuser ationcomponentsthatwillbedeliveredalongwiththeexecutable2.7AssumptionsandAnassumptionisastatementthatisbelievedtobetrueintheabsenceofproofordefinitiveIdentifyanydependenciestheprojecthasonexternalfactorsoutsideitscontrol/6-System3.xSystemFeatureStatethenameofthefeatureinjustafew3.x.1DescriptionandProvideashortdescriptionofthefeatureandindicatewhetheritisofhigh,medium,orlow6-SystemFeatures3.x.2Stimulus/ResponseListthesequencesofinputstimuli(useractions,signalsfromexternaldevices,orothertriggers)andsystemresponsesthatdefinethebehaviorsforthisfeature.3.x.3FunctionalItemizethedetailedfunctionalrequirementsassociatedwiththisfeature./6-ExternalInterface4.1UserDescribethelogicalcharacteristicsofeachuserinterfacethatthesystemneeds.Somepossibleitemstoinclude4.2HardwareDescribethecharacteristicsofeachinterfacebetweenthesoftwareandhardwarecomponentsofthesystem.6-4.ExternalInterfaceRequirements4.3SoftwareDescribetheconnectionsbetweenthisproductandothersoftwarecomponents(identifiedbynameandversion),includingdatabases,operatingsystems,tools,libraries,andintegratedcommercial4.4CommunicationsStatetherequirementsforanycommunicationfunctionstheproductwilluse,includinge-mail,Webbrowser,networkcommunicationsprotocols,andelectronicforms./6-5.OtherNonfunctional5.1PerformanceStatespecificperformancerequirementsforvarioussystemoperations.5.2SafetySpecifythoserequirementsthatareconcernedwithpossibleloss,damage,orharmthatcouldresultfromtheuseofthe6-5.OtherNonfunctionalRequirements(cont’d)5.3SecuritySpecifyanyrequirementsregardingsecurity,integrity,orprivacyissuesthataffectaccesstotheproduct,useoftheproduct,andprotectionofdatathattheproductusesor5.4SoftwareQualityStateanyadditionalproductqualitycharacteristicsthatwillbeimportanttoeithercustomersordevelopers./6-6.OtherDefineanyotherrequirementsthatarenotcoveredelsewhereintheSRS.Examplesincludeinternationalizationrequirements(currency,dateformatting,language,internationalregulations,andculturalandpoliticalissues)andlegal6-AppendixA:Appendix ysisAppendixC:IssuesThisisadynamiclistoftheopenrequirementsissuesthatremaintobe6-GuidelinesforWritingThereisnoformulaicwaytowriteexcellentrequirements;thebestteacherisExcellentrequirements sfolloweffectivetechnical-writingstyleguidelinesandemployuserterminologyratherthancomputerjargon.KeepthesuggestionsinAmbiguousTermsto6-SRS6- 6-项目作基于IEEEStandard830模版，确定求规格说明的。6-PlayingbytheASimpleBusinessRuleBusinessRulesandTheSoftwareRequirementsASoftwareRequirementsSpecificationTheDataSoftwareQualityAttributesImportanttoAttributesImportantto6-TheDataAdatadictionary—asharedrepositorythatdefinesthemeaning,datatype,length,format,necessaryprecision,andallowedrangeorlistofvaluesforalldataelementsorattributesusedintheapplication.6-TheDataDictionaryTheinformationinthedatadictionarybindstogetherthevariousrequirementsComparedwithsprinklingdatadefinitionsthroughoutthefunctionalrequirements,aseparatedatadictionarymakesiteasytofindtheinformationyouneed,anditavoidsredundancyandinconsistencies.6-TheDataDictionaryTheitembeingdefinedisshownontheleftsideofanequalsign,withitsdefinitionontheright.Primitivedata6-TheDataDictionaryPrimitivedataAprimitivedataelementisoneforwhichno positionispossibleorRequestID=*a6-digitsystem-generatedsequentialinteger,beginningwith1,thatuniquelyidentifieseachrequest*6-TheDataDictionaryAdatastructureorrecordcontainsmultipledataitems.RequestedChemical=Chemical+Numberof+++Amount+6-TheDataDictionaryIfmultipleinstancesofanitemcanappearinadatastructure,enclosethatitemincurlyRequest=Request+Request+Charge+1:10{Requested6-TheDataDictionaryAdataelementthatcantakeonalimitednumberofdiscretevaluesiscalledanenumeratedprimitive.tyUnits=["grams"|"kilograms"|"milligrams"|*9-charactertextstringindicatingtheunitsassociatedwiththe tyofchemicalrequested*/6-PlayingbytheASimpleBusinessRuleBusinessRulesandTheSoftwareRequirementsASoftwareRequirementsSpecificationTheDataSoftwareQualityAttributesImportanttoAttributesImportantto6-BeyondFunctionality–SoftwareQualityAttributesUsersnaturallyfocusonspecifyingtheirfunctional,orbehavioral,requirements—thethingsthesoftwarewillletthemdo—butthere'smoretosoftwaresuccessthanjustdeliveringtherightfunctionality.Usersalsohaveexpectationsabouthowwelltheproductwillwork.6-BeyondFunctionality–SoftwareQualityAttributes(cont’d)Characteristicsthatfallintothiscategoryincludehoweasyitistouse,howquicklyitruns,howoftenitfails,andhowithandlesunexpectedconditions.Suchcharacteristics,collectivelyknownassoftwarequalityattributesorqualityfactors,arepartofthesystem'snonfunctional(alsocallednonbehavioral)6-BeyondFunctionality–SoftwareQualityAttributes(cont’d)Qualityattributesaredifficulttodefine,yetoftentheydistinguishaproductthatmerelydoeswhatit'ssupposedtofromonethatdelightsitscustomers.6-BeyondFunctionality–SoftwareQualityAttributes(cont’d)AsRobertCharette(1990)pointedout,"Inrealsystems,meetingthenonfunctionalrequirementsoftenismoreimportantthanmeetingthefunctionalrequirementsinthedeterminationofasystem'sperceivedsuccessorfailure."Excellentsoftwareproductsreflectanoptimumbalanceofcompetingquality6-BeyondFunctionality–SoftwareQualityAttributes(cont’d)Fromatechnical ,qualityattributesdrivesignificantarchitecturalanddesigndecisions,suchaspartitioningsystemfunctionsontovariouscomputerstoachieveperformanceorintegrityobjectives.It'sfarmoredifficultandcostlytorearchitectacompletedsystemtoachieveessentialqualitygoalsthantodesignforthemattheoutset.6-BeyondFunctionality–SoftwareQualityAttributes(cont’d)Customersgenerallydon'tpresenttheirqualityexpectationsexplicitly,althoughtheinformationtheyprovideduringelicitationssomecluesaboutwhattheyhaveinmind.Thetrickistopindownjustwhattheusersarethinkingwhentheysaythesoftwaremustbeuser-friendly,fast,reliable,or6-SoftwareQualityImportantPrimarilytoUsers

ImportantPrimarilytoDevelopers6-SoftwareQualityAttributesDifferentpartsoftheproductneeddifferentcombinationsofqualityattributes.Efficiencymightbecriticalforcertaincomponents,whileusabilityisparamountforDifferentiatequalitycharacteristicsthatapplytotheentireproductfromthosethatarespecifictocertaincomponents,certainuserclasses,orparticularusagesituations.6-SoftwareQualityAttributes anyglobalqualitygoalsinsection5.4oftheSRStemplate,andassociatespecificgoalswithindividualfeatures,usecases,orfunctional6-DefiningQuality ystscandevelopseveralpromptingquestionsbasedoneachattributethattheythoughtmightbe6-DefiningQualityForexample,toexploreintegritythey"Howimportantisittopreventusersfromviewingorderstheydidn'tplace?"or"Shouldeveryonebeabletosearchthestockroominventory?"Theyaskedtheuserrepresentativestorankeachattributeonascaleof1(don'tgiveitanotherthought)to5(critically6-PlayingbytheASimpleBusinessRuleBusinessRulesandTheSoftwareRequirementsASoftwareRequirementsSpecificationTheDataSoftwareQualityAttributesImportanttoAttributesImportantto6-AttributesImportantto6-Availabilityisameasureoftheplanneduptimeduringwhichthesystemisactuallyavailableforuseandfullyoperational.Moreformally,availabilityequalsthemeantimetofailure(MTTF)forthesystemdividedbythesumoftheMTTFandthemeantimetorepairthesystemafterafailureisencountered.Availability

MTTF+MTTR6-AvailabilityAV-1Thesystemshallbeatleast99.5percentavailableonweekdaysbetween6:00a.m.andmidnightlocaltime,andat99.95percentavailableonweekdaysbetween4:00p.m.and6:00p.m.localtime.6-Efficiencyisameasureofhowwellthesystemutilizesprocessorcapacity,diskspace,memory,orcommunicationbandwidth(Davis1993).Efficiencyisrelatedtoperformance,anotherclassofnonfunctionalrequirement,whichisdiscussedlater.6-EfficiencyEF-1.Atleast25percentoftheprocessorcapacityandRAMavailabletotheapplicationshallbeunusedattheplannedpeakload6- Alsoknownasextensibility,augmentability,extendability,andexpandability,flexibilitymeasureshoweasyitistoaddnewcapabilitiestothe6-FL-1.Amaintenanceprogrammerwhohasatleastsixmonthsofexperiencesupportingthisproductshallbeabletomakeanewoutputdeviceavailabletotheproduct,includingcodemodificationsandtesting,withnomorethanonehouroflabor.6- passessecurity,dealswithblockingunauthorizedaccesstosystemfunctions,preventinginformationloss,ensuringthatthesoftwareisprotectedfrom infection,andprotectingtheprivacyandsafetyofdataenteredintothesystem.6-IntegrityIN-1.OnlyuserswhohaveAuditoraccessprivilegesshallbeabletoviewcustomertransactionhistories./6-Interoperabilityindicateshoweasilythesystemcanexchangedataorserviceswithothersystems.6-InteroperabilityIO-1.TheChemicalTrackingSystemshallbeabletoimportanyvalidchemicalstructurefromtheChemiDraw(version2.3orearlier)andChem-Struct(version5orearlier)tools./6-Theprobabilityofthesoftwareexecutingwithoutfailureforaspecificperiodoftimeisknownasreliability(Musa,Iannino,andOkumoto1987).Robustnessissometimesconsideredanaspectofreliabil