requirements engineering - quality models
TRANSCRIPT
Requirements Engineering:
Quality Models
CECS 542
Dr.BirgitPenzenstadler 1
Photocredit:Ma7hewKane,Unsplash
Mo=va=on
Dr.BirgitPenzenstadler 2
[GonçaloBorrêga:Thetruthaboutnon-func=onalrequirements.Blogentry,2013.h7p://www.outsystems.com/blog/2013/03/the-truth-about-non-func=onal-requirements-nfrs.html]
Func=onalRequirementsandTheirPoorCousins:TheTruthAboutNFRs
Dr.BirgitPenzenstadler 3
• WheneveranybodysaysFunc=onalRequirement,Ithinkofprincesses.IthinkofArielleandCinderella.Ithinkofhoweachiscentraltoherstoryandembodiesaspecificiden=ty,andthenIthinkoftheprincesswhostandsoutasatruemetaphorforfunc=onalrequirements–theonewhoreflectstheroleperfectly.IthinkofSnowWhite.
• SnowWhiteisafunc=onalrequirementifIeversawone.Sheisatoncecentraltoherstory,itsmainprotagonist,itsraisond’etre,yetsurroundedbyahostofsuppor=ngcharacters–dwarfs–whoserolesarenecessaryforthestorytobecomplete.Nodwarfs,norealstory.It’sthatsimple.Ifasingledwarfismissing,theen=restoryiscompromised.SnowWhiteiscompromised.
[GonçaloBorrêga:Thetruthaboutnon-func=onalrequirements.Blogentry,2013.h7p://www.outsystems.com/blog/2013/03/the-truth-about-non-func=onal-requirements-nfrs.html]
Dr.BirgitPenzenstadler 4
• Andit’snearlythesamewithapplica=ons.Ifanapplica=onisthestoryandSnowWhiteisthefunc=onalrequirement,thenwecanthinkofdwarfsasnon-func=onalrequirements(NFRs).IfasingleNFRismissingfromanapplica=onthenthatapplica=oniscompromised.Deployingasquirrelyapplica=onisthesameasaddingmaintenanceissuesandtechnicaldebtdirectlytoyourapplica=onpor`olio.Eventually,thatapplica=onwillhavetobeaddressed,thoseNFRswillhavetobeadded,andtheITdepartmentwhodeployedtheappwillhavetocontendwiththecostofchangingsobware.
• Howdoesthishappen?ChangingandmaintainingsobwareishardandthereforeexpensivetodoandITdepartmentsareobenrushedorunderfunded.However,iftheyareina‘Justdoit’modethenthoseopera=onal,non-func=onalrequirementsthatmakeanapplica=oncompleteareeasytoleaveoutorare‘forgo7en.’TheconsequencesofleavingtheseNFRsoutofanapplica=onleaddirectlytotheaforemen=onedmaintenanceproblemsandincreasedtechnicaldebt.
• Here’sthelistofmostcommonNFRsthatweseeourcustomersworryingabout:
Func=onalRequirementsandTheirPoorCousins:TheTruthAboutNFRs
[GonçaloBorrêga:Thetruthaboutnon-func=onalrequirements.Blogentry,2013.h7p://www.outsystems.com/blog/2013/03/the-truth-about-non-func=onal-requirements-nfrs.html]
Dr.BirgitPenzenstadler 5
CommonNFRs
[GonçaloBorrêga:Thetruthaboutnon-func=onalrequirements.Blogentry,2013.h7p://www.outsystems.com/blog/2013/03/the-truth-about-non-func=onal-requirements-nfrs.html]
Dr.BirgitPenzenstadler 6
CommonNFRs
[GonçaloBorrêga]
Dr.BirgitPenzenstadler 7
CommonNFRs
[GonçaloBorrêga]
Dr.BirgitPenzenstadler 8
CommonNFRs
[GonçaloBorrêga]
Dr.BirgitPenzenstadler 9
CommonNFRs
[GonçaloBorrêga]
Dr.BirgitPenzenstadler 10
Func=onalRequirementsandTheirPoorCousins:TheTruthAboutNFRs
• LikeSnowWhite’sdwarfstheseNFRsarenecessarytocomple=ngthestoryoftheapplica=on.Whileyoumightconsider2or3importantNFRsforaproject(likeperformanceandsecurity),you’llprobablynotcovertheothersextensivelyenough,oryoumightmissoutonthemalltogether.
• Andifyoudoallocate=metodealwiththemall,whentheprojectscheduleslips,theNFRsmaybethefirstthingyou’lldrop…becausenoonereallyseesthem,andyourteamwillbelookingatthefunc=onalrequirementsinstead.
• So,whetheryouplanforNFRsornot,chancesarehighyouwon’tcoverthem100%ofthe=meinyourdevelopmentproject.You’llcompromiseandnotthinkofthewholestory–thewholeapplica=on.
• Butyoushouldtry.Youshouldtrytoavoidaddingtechnicaldebtandmaintenancenightmarestoyourfuturepor`oliowheneverpossible.Thecostofchangeisreal,andthemomentyoudeployyourapp,you’llhavetoaddressitsproblems.
• FromyourexperiencewhataretheNFRsyouconstantlyseedevelopersandprojectteamsdroppingmostoben?
QualitymodelsanddealingwithNFRs
• UsageofQualitymodelsinRE• Exemplaryqualitymodels• DealingwithNFRsinAMDiRE
Dr.BirgitPenzenstadler 11
KRayker,stock.xchng
UsageofqualitymodelsinRE
12
Whatarequalitymodels?à Conceptualmodelsforthedescrip=onofquality.
UsageofqualitymodelsinRE• Defini=onandassessmentofsobwarequality–beginninginRE
• Qualityassurance,forexampleofartefactsinRE• Also:Classifica=onofrequirementsaccordingtocharacteris=cs
UsageofqualitymodelsinRE
13
Classifica=ononthebasisofqualitymodels• Classifica=onofnon-func=onrequirementsaccordingto
characteris=cs.– Whichdifferentclassesofrequirementsexist?– Whichaspectsareimportanttoconsider?– Whichmodelingconceptsandinterdependenciesareimportanttoconsider?
Delimita=on:Artefactmodels• Ideallybuildonqualitymodels
(comparetosystemmodels)à Conceptmodel(ContentModel)à Structureoftheconceptmodel
(StructureModel)
Artefact-based RE Approach for Business Information Systems (Basic Components)
StructureModel
Artefact Model
ContentModel
Role Model
Process Model
Tool SupportCustomisation Approach
Met
a M
odel
RE
Ref
eren
ce M
odel
Structure Content
Proj
ect-s
peci
fic
Exem
plar
s
inst
ance
of
inst
ance
of
!
PRODUKT.PROJEKTBEZEICHNUNG - PRODUKT.NAME
Zuletzt geändert: 27.10.2010 13:28 3/20
Content
1! Introduction .......................................................................................................................... 6!
1.1! Overview ....................................................................................................................... 6!
1.2! Purpose .......................................................................................................................... 6!
1.3! References ..................................................................................................................... 7!
1.4! Scope ............................................................................................................................. 8!
2! System Vision ...................................................................................................................... 8!
2.1! Summary of Business Specification.............................................................................. 8!
2.2! Scope of Information System under Consideration ...................................................... 8!
2.2.1! System Overview ................................................................................................... 8!
2.2.2! External Systems .................................................................................................. 10!
2.2.3! Use Case Overview .............................................................................................. 10!
2.2.4! Information System Service Overview ................................................................ 10!
3! Information System Requirements..................................................................................... 11!
3.1! Actors .......................................................................................................................... 11!
3.2! Generic Scenarios........................................................................................................ 11!
3.3! Domain-specific Application Capabilities .................................................................. 12!
3.3.1! <<Business Domain>> <Name>.......................................................................... 12!
3.4! Information System Objects........................................................................................ 14!
3.5! System Quality Requirements..................................................................................... 16!
3.6! Architectural Constraints............................................................................................. 16!
3.6.1! Logical Restrictions.............................................................................................. 17!
3.6.2! Technical Restrictions .......................................................................................... 17!
4! Integrational Requirements ................................................................................................ 18!
4.1! Deployment Requirements.......................................................................................... 18!
4.2! Migration Requirements.............................................................................................. 18!
5! Organisational Requirements ............................................................................................. 19!
5.1! Project Requirements .................................................................................................. 19!
5.2! Obligations .................................................................................................................. 19!
5.3! Glossary....................................................................................................................... 19!
6! Abbreviations ..................................................................................................................... 20!
7! References .......................................................................................................................... 20!
Travel Ordering System
Requirements Specification
Version: 0.1
Project Name <Name>
Project Lead <Name>
Responsible <Name>
Created on <Date>
Last changed
X In process
Submitted
State
Completed
Document File
V-Modell XT Version VMRELEASE 1.3with BISA Extension
illustrative
Met
a M
odel
RE
Ref
eren
ce M
odel
Structure Content
Proj
ect-s
peci
fic
Exem
plar
s
inst
ance
of
inst
ance
of
!
PRODUKT.PROJEKTBEZEICHNUNG - PRODUKT.NAME
Zuletzt geändert: 27.10.2010 13:28 3/20
Content
1! Introduction .......................................................................................................................... 6!
1.1! Overview ....................................................................................................................... 6!
1.2! Purpose .......................................................................................................................... 6!
1.3! References ..................................................................................................................... 7!
1.4! Scope ............................................................................................................................. 8!
2! System Vision ...................................................................................................................... 8!
2.1! Summary of Business Specification.............................................................................. 8!
2.2! Scope of Information System under Consideration ...................................................... 8!
2.2.1! System Overview ................................................................................................... 8!
2.2.2! External Systems .................................................................................................. 10!
2.2.3! Use Case Overview .............................................................................................. 10!
2.2.4! Information System Service Overview ................................................................ 10!
3! Information System Requirements..................................................................................... 11!
3.1! Actors .......................................................................................................................... 11!
3.2! Generic Scenarios........................................................................................................ 11!
3.3! Domain-specific Application Capabilities .................................................................. 12!
3.3.1! <<Business Domain>> <Name>.......................................................................... 12!
3.4! Information System Objects........................................................................................ 14!
3.5! System Quality Requirements..................................................................................... 16!
3.6! Architectural Constraints............................................................................................. 16!
3.6.1! Logical Restrictions.............................................................................................. 17!
3.6.2! Technical Restrictions .......................................................................................... 17!
4! Integrational Requirements ................................................................................................ 18!
4.1! Deployment Requirements.......................................................................................... 18!
4.2! Migration Requirements.............................................................................................. 18!
5! Organisational Requirements ............................................................................................. 19!
5.1! Project Requirements .................................................................................................. 19!
5.2! Obligations .................................................................................................................. 19!
5.3! Glossary....................................................................................................................... 19!
6! Abbreviations ..................................................................................................................... 20!
7! References .......................................................................................................................... 20!
Travel Ordering System
Requirements Specification
Version: 0.1
Project Name <Name>
Project Lead <Name>
Responsible <Name>
Created on <Date>
Last changed
X In process
Submitted
State
Completed
Document File
V-Modell XT Version VMRELEASE 1.3with BISA Extension
illustrative
Met
a M
odel
RE
Ref
eren
ce M
odel
Structure Content
Proj
ect-s
peci
fic
Exem
plar
s
inst
ance
of
inst
ance
of
!
PRODUKT.PROJEKTBEZEICHNUNG - PRODUKT.NAME
Zuletzt geändert: 27.10.2010 13:28 3/20
Content
1! Introduction .......................................................................................................................... 6!
1.1! Overview ....................................................................................................................... 6!
1.2! Purpose .......................................................................................................................... 6!
1.3! References ..................................................................................................................... 7!
1.4! Scope ............................................................................................................................. 8!
2! System Vision ...................................................................................................................... 8!
2.1! Summary of Business Specification.............................................................................. 8!
2.2! Scope of Information System under Consideration ...................................................... 8!
2.2.1! System Overview ................................................................................................... 8!
2.2.2! External Systems .................................................................................................. 10!
2.2.3! Use Case Overview .............................................................................................. 10!
2.2.4! Information System Service Overview ................................................................ 10!
3! Information System Requirements..................................................................................... 11!
3.1! Actors .......................................................................................................................... 11!
3.2! Generic Scenarios........................................................................................................ 11!
3.3! Domain-specific Application Capabilities .................................................................. 12!
3.3.1! <<Business Domain>> <Name>.......................................................................... 12!
3.4! Information System Objects........................................................................................ 14!
3.5! System Quality Requirements..................................................................................... 16!
3.6! Architectural Constraints............................................................................................. 16!
3.6.1! Logical Restrictions.............................................................................................. 17!
3.6.2! Technical Restrictions .......................................................................................... 17!
4! Integrational Requirements ................................................................................................ 18!
4.1! Deployment Requirements.......................................................................................... 18!
4.2! Migration Requirements.............................................................................................. 18!
5! Organisational Requirements ............................................................................................. 19!
5.1! Project Requirements .................................................................................................. 19!
5.2! Obligations .................................................................................................................. 19!
5.3! Glossary....................................................................................................................... 19!
6! Abbreviations ..................................................................................................................... 20!
7! References .......................................................................................................................... 20!
Travel Ordering System
Requirements Specification
Version: 0.1
Project Name <Name>
Project Lead <Name>
Responsible <Name>
Created on <Date>
Last changed
X In process
Submitted
State
Completed
Document File
V-Modell XT Version VMRELEASE 1.3with BISA Extension
illustrative
Organisational LevelProcess Integration
Project LevelStatic Tailoring
Dynamic Tailoring
...
Project Scope defined
System Specificationaccepted
...
Business Analyst...
Requirements Engineer
Context Specification
Requirements Specification
System Specification
QualitymodelsanddealingwithNFRs
• UsageofQualitymodelsinRE• Exemplaryqualitymodels• DealingwithNFRsinAMDiRE
Dr.BirgitPenzenstadler 14
KRayker,stock.xchng
Excursion:QualitymodelsQualitymodels• Determinewhichqualityaspectsandconceptsexistandhowtheseare
related• Supportthestructuredelicita=onandmodelingofqualityrequirementsà E.g.viaataxonomyofqualitya7ributesExamples:• Classifica=onacc.toBoehm(1978)• IEEE29148SobwareRequirements
Documenta=onStandard(2011)• ISO/IEC9126(1993,revised2001)• TUMS&SEQualityModelChallenges:
– Manydifferentqualityaspectsandrela=onsbetweenthem
– Systema=csintheirapplica=oninRE(aswellasapplica=oninassessment)
15
[ISOStd.](Excerpt)
Example:Taxonomyofqualitya7ributes(QuaMoCo)
Ins-tutfürInforma-kChairIV:So8ware&SystemsEngineering 16
Assessmentofqualitymodels• Exemplaryqualitymodelsdeterminethetaxonomyofqualitycriteriaanda7ributes
Cri=calaspects• Themodelsobenstayontheabstractlevelof„-ili=es“à Nostatementaboutmeasurabilityandassessmentofqualitycriteria
• NodirectapplicabilitytoRE– Nocluesforexplicitdeduc=onofrequiredsystemcharacteris=csExample:Thedemandformul=-languagedocumenta=onsupportsmaintainability,butalsousability.
– Othernon-func=onalaspectsareobennotcovered
17But:qualitymodelsarethebasisfortheclassifica=onofNFRs.
NFRTaxonomyacc.toAxelvanLamsweerde
18
ATMExamplesforNFRTaxonomybyLamsweerde
19
-Securityofpersonalizeddata-AvailabilityoftheAMT-...
ThesecurityconcepthastoadheretoIEC61508Standard.(àadequatearchitecture)
TheATMusesdataencryp=on.
Thefullfunc=onalityshallbeavailablebyMay2014.
ISO25010
• Internalquality:mainlyvisibleinthecode,e.g.reusabilityofthecodewithinmaintainability
• Externalquality:mainlycharacteris=csthatcanbeseenfromoutsidethesystembutnotnecessarilybytheuser
• Qualityinuse:perceivedbytheuserofthesystemduringrun=me
Dr.BirgitPenzenstadler 20
ISO25010
ISO25010
Summary
23
Whatarequalitymodels?à Conceptualmodelsforthedescrip=onofquality.
UsageofqualitymodelsinRE§ Defini=onandassessmentofsobwarequality–beginninginRE§ Qualityassurance,forexampleofartefactsinRE§ Also:Classifica=onofrequirementsaccordingtocharacteris=cs
Examples§ QuaMoCo§ Lamsweerdetaxonomy§ ISO25010