Page ‹#›Information Systems Analysis and Design csc3402004 John Mylopoulos Non-Functional Requirements -- 1XIV. Non-Functional RequirementsXIV. Non-Functional RequirementsClassification ofClassification of NFRs NFRsCriteria and FactorsCriteria and FactorsPortability, Reliability, PerformancePortability, Reliability, PerformanceExample NFR for an Automated Money MachineExample NFR for an Automated Money MachineInformation Systems Analysis and Design csc3402004 John Mylopoulos Non-Functional Requirements -- 2Non-Functional Requirements --Non-Functional Requirements --NFRsNFRs (also Software Qualities) (also Software Qualities) Define global constraints on a software system, such asdevelopment costs, operational costs, performance,reliability, maintainability, portability, robustness etc. Should not be confused with functional requirementsfunctional requirements,which impose requirements on the function of a system Are generally stated informally, are often contradictory,difficult to enforce during development and to evaluate forthe customer prior to deliveryHow do we classify them?How do we classify them?Information Systems Analysis and Design csc3402004 John Mylopoulos Non-Functional Requirements -- 3Types of Types of NFRsNFRsInterface requirementsInterface requirements -- how will the systeminterface with its environment, users and other systems;e.g., "user-friendliness”.Performance requirementsPerformance requirements:time/space boundstime/space bounds, such as workloads, responsetime, throughput and available storage space, e.g.,"system must handle 1,000 transactions/sec");reliabilityreliability -- availability of components and integrityof data, e.g., "less than 1hr downtime/yr"securitysecurity, permissible access to data and operations;survivabilitysurvivability, such as system will survive fire,natural catastrophes.Operating requirementsOperating requirements -- include physical constraints(size, weight), personnel availability, skill levels...Information Systems Analysis and Design csc3402004 John Mylopoulos Non-Functional Requirements -- 4Types of Types of NFRs NFRs (cont(cont’’d)d)Lifecycle requirementsLifecycle requirements -- can be classified under twosub-categories:Quality of the design, such as maintenability,enhanceability, portability; expected market orproduct lifespan,...(these don't affect initial systembut may lead to increased maintenance costs orearly obsolescence.)Limits on development, other software lifecyclephases, such as development time limitations,resource availability, methodological standards etc.Economic requirementsEconomic requirements -- immediate and/or long-term costs.Information Systems Analysis and Design csc3402004 John Mylopoulos Non-Functional Requirements -- 5Acquisition Concern User Concern Quality FactorsPerformance Resource utilization efficiencysecurity, confidence, integrityperformance under reliabilityadversity, ease-of-use survivabilityusabilityDesign Conform to reqs?... correctnesseasy to repair?... maintenabilityverified performance? verifiabilityAdaptation Easy to expand? expandability...upgrade function or flexibilityperformance? interoperability...change?...interface portabilitywith another system? reusability...port?...use in anotherapplication?Acquisition ConcernAcquisition Concern User ConcernUser Concern Quality FactorsQuality FactorsPerformancePerformance Resource utilizationResource utilization efficiencyefficiencysecurity, confidence,security, confidence, integrityintegrityperformance underperformance under reliabilityreliabilityadversity, ease-of-useadversity, ease-of-use survivabilitysurvivabilityusabilityusabilityDesignDesign Conform toConform to reqs reqs?...?... correctnesscorrectnesseasy to repair?...easy to repair?... maintenabilitymaintenabilityverified performance?verified performance? verifiabilityverifiabilityAdaptationAdaptation Easy to expand?Easy to expand? expandabilityexpandability...upgrade function or...upgrade function or flexibilityflexibilityperformance?performance? interoperabilityinteroperability...change?...interface...change?...interface portabilityportabilitywith another system?with another system? reusabilityreusability...port?...use in another...port?...use in anotherapplication?application?(Different) Classification of (Different) Classification of NFRsNFRsInformation Systems Analysis and Design csc3402004 John Mylopoulos Non-Functional Requirements -- 6Factors and Criteria FactorsFactors are customer-related concerns, such asefficiency, integrity, reliability, correctness, survivability,usability,... CriteriaCriteria -- technical (development-oriented) concernssuch as anomaly management, completeness,consistency, traceability, visibility,... Each factor depends on associated criteria, e.g.,CorrectnessCorrectness depends on completenesscompleteness, consisteconsiste--ncyncy, traceabilitytraceability,...VerifiabilityVerifiability depends on modularitymodularity, self-descriptionself-descriptionand simplicitysimplicityPage ‹#›Information Systems Analysis and Design csc3402004 John Mylopoulos Non-Functional Requirements -- 7(…Two Year ago…)Canada - USA 5-2 Information Systems Analysis and Design csc3402004 John Mylopoulos Non-Functional Requirements -- 8EfficiencyIntegrityReliabilitySurvivabilityUsabilityCorrectnessVerifiabilityFlexibilityPortabilityReusabilityAccuracyAnomaly MngtAutonomyDistributednessEffectiveness storageOperabilitySystem accessibilityTrainingCompletenessConsistencyTraceabilityVisibilityXXXXXXXXXXXXXFactorsCriteriaPerformance Design AdaptationPerformanceDesignfactorsfactors -- customer-related concernscriteriacriteria -- technicalconcernsFactorsFactors vs vs Criteria Criteria(Partial table)Information Systems Analysis and Design csc3402004 John Mylopoulos Non-Functional Requirements -- 9Applic. independenceAugmentabilityCommonalityDoc. accessibilityFunctional overlapFunctional scopeGeneralityIndependenceSystem claritySystem compatibilityModularitySelf descriptivenessSimplicityXXXXXXXXXXXXXXXXXXXXXAdaptationGeneralEfficiencyIntegrityReliabilitySurvivabilityUsabilityCorrectnessVerifiabilityFlexibilityPortabilityReusabilityFactorsCriteriaPerformance Design Adaptation(Partial table)Information Systems Analysis
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