Information Systems Analysis and Design csc340 Information Systems Analysis and Design XIV Non Functional Requirements csc340 Non Functional Requirements NFRs also Software Qualities Classification of NFRs Criteria and Factors Portability Reliability Performance Example NFR for an Automated Money Machine Define global constraints on a software system such as development costs operational costs performance reliability maintainability portability robustness etc Should not be confused with functional requirements 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 for the customer prior to delivery How do we classify them 2004 John Mylopoulos Non Functional Requirements 1 Information Systems Analysis and Design csc340 2004 John Mylopoulos Non Functional Requirements 2 Information Systems Analysis and Design csc340 Types of NFRs Types of NFRs cont cont d Interface requirements how will the system interface with its environment users and other systems e g user friendliness Performance requirements time space bounds such as workloads response time throughput and available storage space e g system must handle 1 000 transactions sec reliability availability of components and integrity of data e g less than 1hr downtime yr security permissible access to data and operations survivability such as system will survive fire natural catastrophes Operating requirements include physical constraints size weight personnel availability skill levels Lifecycle requirements can be classified under two sub categories Quality of the design such as maintenability enhanceability portability expected market or product lifespan these don t affect initial system but may lead to increased maintenance costs or early obsolescence Limits on development other software lifecycle phases such as development time limitations resource availability methodological standards etc Economic requirements immediate and or longterm costs 2004 John Mylopoulos Non Functional Requirements 3 Information Systems Analysis and Design csc340 2004 John Mylopoulos Information Systems Analysis and Design Different Classification of NFRs Acquisition Concern AcquisitionConcern Concern User User Concern Concern Quality QualityFactors Factors Performance Performance Resource utilization Resourceutilization utilization security security confidence confidence performance under performanceunder under adversity ease of use adversity ease of use ease of use efficiency efficiency integrity integrity integrity reliability reliability reliability survivability survivability usability usability Design Design Conform reqs Conformtotoreqs reqs easy easyto torepair repair verified verifiedperformance performance correctness correctness correctness maintenability maintenability maintenability verifiability verifiability verifiability Adaptation Adaptation Easy expand Easyto toexpand expand upgrade function or upgradefunction functionor or performance performance change interface change interface with withanother anothersystem system port use ininanother another port usein another application application expandability expandability flexibility flexibility interoperability interoperability interoperability portability portability reusability reusability 2004 John Mylopoulos Non Functional Requirements 4 csc340 Factors and Criteria Factors are customer related concerns such as efficiency integrity reliability correctness survivability usability Criteria technical development oriented concerns such as anomaly management completeness consistency traceability visibility Each factor depends on associated criteria e g Correctness depends on completeness consisteconsistency traceability Verifiability depends on modularity modularity self description and simplicity Non Functional Requirements 5 2004 John Mylopoulos Page Non Functional Requirements 6 Information Systems Analysis and Design csc340 Information Systems Analysis and Design csc340 Factors vs Criteria Performance Design Criteria Performance Accuracy X Anomaly Mngt X X Autonomy X Distributedness X Effectiveness storage X Operability X X System accessibility Training X Design Completeness X Consistency X Traceability X Visibility X 2004 John Mylopoulos Non Functional Requirements 7 Information Systems Analysis and Design csc340 2004 John Mylopoulos Flexibility Adaptation Applic independence Augmentability Commonality Doc accessibility Functional overlap Functional scope Generality Independence System clarity System compatibility General Modularity Self descriptiveness Simplicity Quality Quality Speed Speed Size Size X X Ease Easeof ofUse Use X X X X X Reliability Reliability Robustness Robustness X X X X X X X X X X X Portability Portability Non Functional Requirements 9 Information Systems Analysis and Design csc340 csc340 Metric Metric transactions sec transactions sec response responsetime time KBytes KBytes number numberof ofRAM RAMchips chips training trainingtime time number numberof ofhelp helpframes frames mean time between failures mean time between failures probability probability of ofunavailability unavailability rate rateof offailure failure availability availability time timeto torestart restartafter afterfailure failure percentage percentageof ofevents eventscausing causingfailure failure percentage percentageof oftarget dependent target dependentstatements statements number numberof oftarget targetsystems systems 2004 John Mylopoulos Non Functional Requirements 10 Information Systems Analysis and Design Portability csc340 Reliability Portability is the degree to which software running on one platform can easily be converted to run on another Portability is hard to quantify because it is hard to predict on what other platforms will the software be required to run Portability for a given software system can be enhanced by using languages operating systems and tools that are universally available and standardized such as FORTRAN COBOL or C for languages or such as Unix Windows or OS 2 operating systems Portability requirements should be given priority for systems that may have to run on different platforms in the near future 2004 John Mylopoulos Partial table Non Functional Requirements 8 Quality Metrics X X factors customerrelated concerns criteria technical concerns Information Systems Analysis and Design Design Adaptation X Adaptation 2004 John Mylopoulos
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