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NonNon--Functional RequirementsFunctional Requirements

Lawrence ChungLawrence Chung

Department of Computer ScienceDepartment of Computer Science The University of Texas at DallasThe University of Texas at Dallas NonNon--Functional RequirementsFunctional Requirements Practices and Recommendations: Practices and Recommendations:

A Brief SynopsisA Brief Synopsis

Why What

Some Classification Schemes

?NFRs and RE Processes?

Product-Oriented Approach: Some Individual NFRs

The NFR Framework

Appendix?

With Rational Unified Process and UML

With Volere Requirements Specification Templates

Others

Why Why

NonNon--Functional Requirements (NFRsFunctional Requirements (NFRs

Consider a brochure from an automobile manufacturer:Consider a brochure from an automobile manufacturer:■■When you buy our car, you can now drive to a store...When you buy our car, you can now drive to a store...

Lawrence Chung

Consider a brochure from a cellular phone manufacturer:Consider a brochure from a cellular phone manufacturer:■■When you buy our cellular phone, you can now call your When you buy our cellular phone, you can now call your friend.friend.

■■Well, ...Well, ... With cellular phones:With cellular phones:"... enhancements enable the "... enhancements enable the best possiblebest possible operation operation of your mobile ... in of your mobile ... in various conditionsvarious conditions

The earpiece fits in either ear allowing for The earpiece fits in either ear allowing for convenientconvenient

and and access to access to all basic call controlsall basic call controls . ... To . ... To maximize call securitymaximize call security , the , the

headset also supports ... the wireless connection for headset also supports ... the wireless connection for

compatiblecompatible NF Non-Functional Concerns drive just about everything

headset also supports ... the wireless connection for headset also supports ... the wireless connection for

compatiblecompatible models."models."

With home networking:With home networking:"... is the total home networking solution ... "... is the total home networking solution ...

linking variety of digital home appliances as one. linking variety of digital home appliances as one. It enables you to enjoy It enables you to enjoy

convenientconvenient , , pleasantpleasant , , comfortablecomfortable , and, and living environment living environment at any timeat any time and and any placeany place

Why Why

NFRsNFRs

With CASE tool software:With CASE tool software:■■ The basic function is provision of some servicesThe basic function is provision of some services

"... is a "... is a powerful, easypowerful, easy--toto-- useuseapplication definition platform used by business experts to application definition platform used by business experts to quicklyquicklyassemble functionally assemble functionally richrichsimulations of Websimulations of Web--based applications based applications in a matter of in a matter of hourshours. ... Using the . ... Using the easy to learneasy to learn, drag, drag--andand--drop paradigm ..., business people can drop paradigm ..., business people can quicklyquicklylay out the page flow of simulations and create lay out the page flow of simulations and create high fidelityhigh fidelitypages that pages that preciselypreciselymimic not mimic not only the look and feel of the final application, ..."only the look and feel of the final application, ..."

Lawrence Chung

Software is harder than hardware

But

Soft is harder to deal with than hardNF

F ■■--ilitiesilities

: understandability, usability, modifiability, inter: understandability, usability, modifiability, inter--operability, reliability, operability, reliability,

portability, dependability, flexibility, availability, maintainability, scalability, (reportability, dependability, flexibility, availability, maintainability, scalability, (re--

)configurability, customizability, adaptability, stability, variability, volatility, traceability, )configurability, customizability, adaptability, stability, variability, volatility, traceability,

verifiability, predictability, compatibility, survivability, accessibility, ...verifiability, predictability, compatibility, survivability, accessibility, ...

■■--itiesities

: security, simplicity, clarity, ubiquity, integrity, safety, modularity, nomadicity, ...: security, simplicity, clarity, ubiquity, integrity, safety, modularity, nomadicity, ...What are

Non-Functional Requirements

NFR ■■--itiesities

: security, simplicity, clarity, ubiquity, integrity, safety, modularity, nomadicity, ...: security, simplicity, clarity, ubiquity, integrity, safety, modularity, nomadicity, ...

■■--nessness

: user: user--friendliness, robustness, timeliness, responsiveness, correctness, friendliness, robustness, timeliness, responsiveness, correctness,

completeness, conciseness, cohesiveness, ...completeness, conciseness, cohesiveness, ... ■■...and there are many more...and there are many more : convenience, comfort, performance, : convenience, comfort, performance,

efficiency, accuracy, precision, slim, esthetics, consistency, coherence, fault tolerance, selfefficiency, accuracy, precision, slim, esthetics, consistency, coherence, fault tolerance, self--

healing capability, autonomy, cost, development time, timehealing capability, autonomy, cost, development time, time--toto--market, longmarket, long--lasting battery, lasting battery,

low coupling, ...low coupling, ... subjective, ambiguous, conflicting, global soft

NFRs:NFRs:

IEEE definitionIEEE definition

""non functional requirementnon functional requirement -- in software system in software system

engineering, a software requirement that describes engineering, a software requirement that describes

not whatnot what the the software will do, software will do, but howbut how the software will do it, for example, the software will do it, for example,

software performance requirements, software external interface software performance requirements, software external interface

requirements, design constraints, and software quality attributes. requirements, design constraints, and software quality attributes.

Lawrence Chung

requirements, design constraints, and software quality attributes. requirements, design constraints, and software quality attributes. Nonfunctional requirements are difficult to test; therefore, they Nonfunctional requirements are difficult to test; therefore, they

are usually evaluated subjectively."are usually evaluated subjectively."GeneralGeneral ObservationsObservations

""non functional requirementnon functional requirement -- generally informally stated, generally informally stated,

often contradictory, difficult to enforce during development and often contradictory, difficult to enforce during development and

evaluate for the customer prior to delivery"evaluate for the customer prior to delivery"

NFRs:NFRs:

in both definitions & solutionsin both definitions & solutions Classification 1 Classification 1 [Roman, IEEE Computer 1985][Roman, IEEE Computer 1985] NFR

6 classes + 2-3 levels

Classification is supposed to bring order into chaos, but ...

NFRs:NFRs:

in both definitions & solutionsin both definitions & solutions

Classification 2 Classification 2 -- Process, Product and External considerations Process, Product and External considerations [Sommerville [Sommerville

1992]1992]

NFR

3 classes + 2 levels

Classification 3Classification 3

NFRs:NFRs:

subjectivesubjective in both definitions & solutionsin both definitions & solutions NFR

Note correlations3 classes + 3 levels

FFunctionalityFeature set capabilities, security,

generalityUU sabilityHuman factors aesthetics, consistency, documentation

Frequency/severity of failure,

Dimensions of Quality Dimensions of Quality --Components of Components of

FURPFURP++

[Grady1992][Grady1992] NFR

Classification 4Classification 4

NFRs:NFRs:

subjectivesubjective in both definitions & solutionsin both definitions & solutions4+ classes + 2 levels

RReliability

Frequency/severity of failure,

recoverability, predictability, accuracy, MTBF PP erformanceSpeed efficiency, resource usage, throughput, response timeSSupportabilityTestability Extensibility

Adaptability Maintainability

Compatibility Configurability

Serviceability Installability

Localizability Robustness

Software Quality Tree [Boehm 1976]Software Quality Tree [Boehm 1976] NFR

Classification 5Classification 5

NFRs:NFRs:

subjectivesubjective in both definitions & solutionsin both definitions & solutions

Note correlations2 classes + 3 levels

portabilityreliability general utility as-is utilitymaintainability efficiencyhuman engineeringtestabilityunderstandabilitymodifiability

consistencyaccountabilitydevice efficiencyaccessibilitycommunicativenessself-descriptivenessstructurednessconcisenesslegibilityaugmentability

NFRsNFRs

& RE Processes:& RE Processes:

Why?Why?

Quality of product Quality of product Quality of ProcessQuality of Process Proc ?Garbage in garbage out, so get the right requirements?Garbage thru garbage out,

Lawrence Chung

Product

quotesdbs_dbs7.pdfusesText_5

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