2. Sofware process and models FOR THE UNIT

SOFTWARE PROCESS

1. 20CS502:SOFTWARE PROCESS
Mrs.S.VIJAYASHARMILA,
AP/IT
KLNCE

2. What / who / why is Process Models?
What:Gothroughaseriesofpredictablesteps---aroadmapthathelpsyoucreateatimely,
high-qualityresults.
Who:Softwareengineersandtheirmanagers,clientsalso.Peopleadapttheprocesstotheir
needsandfollowit.
Why:Providesstability,control,andorganizationtoanactivitythatcanifleft
uncontrolled,becomequitechaotic.However,modernsoftwareengineeringapproaches
mustbeagileanddemandONLYthoseactivities,controlsandworkproductsthatare
appropriate.
WhatWorkproducts:Programs,documents,anddata
Whatarethesteps:Theprocessyouadoptdependsonthesoftwarethatyouarebuilding.
Oneprocessmightbegoodforaircraftavionicsystem,whileanentirelydifferentprocess
wouldbeusedforwebsitecreation.
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3. Definition of Software Process
Aframeworkfortheactivities,actions,andtasksthatarerequiredto
buildhigh-qualitysoftware.
SoftwareProcess(SP)definestheapproachthatistakenassoftwareis
engineered.
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4. A Generic Process Model
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5. A Generic Process Model
Aswediscussedbefore,agenericprocessframeworkforsoftware
engineeringdefinesfiveframeworkactivities
communication,planning,modeling,construction,anddeployment.
Inaddition,asetofumbrellaactivitiesareappliedthroughouttheprocess.
projecttrackingandcontrol,riskmanagement,qualityassurance,
configurationmanagement,technicalreviews,andothers
Nextquestionis:
Howtheframeworkactivitiesandtheactionsandtasksthatoccur
withineachactivityareorganizedwithrespecttosequenceandtime?
Seetheprocessflowforanswer.
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6. Process Flow Types
Linearprocessflowexecuteseachofthefiveactivitiesinsequence.
Aniterativeprocessflowrepeatsoneormoreoftheactivitiesbefore
proceedingtothenext.
Anevolutionaryprocessflowexecutestheactivitiesinacircular
manner.Eachcircuitleadstoamorecompleteversionofthe
software.
Aparallelprocessflowexecutesoneormoreactivitiesinparallel
withotheractivities(modelingforoneaspectofthesoftwarein
parallelwithconstructionofanotheraspectofthesoftware).
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7. Process Flow
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8. Identifying a Task Set
Beforeyoucanproceedwiththeprocessmodel,akeyquestion:
whatactionsareappropriateforaframeworkactivitygiventhe
natureoftheproblem,thecharacteristicsofthepeopleandthe
stakeholders?
Atasksetdefinestheactualworktobedonetoaccomplishthe
objectivesofasoftwareengineeringaction.
Alistofthetaskstobeaccomplished
Alistoftheworkproductstobeproduced
Alistofthequalityassurancefilterstobeapplied
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9. Identifying a Task Set -Example
Forexample,asmallsoftwareprojectrequestedbyonepersonwith
simplerequirements,thecommunicationactivitymightencompass
littlemorethanaphoneallwiththestakeholder.Therefore,theonly
necessaryactionisphoneconversation,theworktasksofthisaction
are:
1.Makecontactwithstakeholderviatelephone.
2.Discussrequirementsandtakenotes.
3.Organizenotesintoabriefwrittenstatementofrequirements.
4.E-mailtostakeholderforreviewandapproval.
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10. Example of a Task Set for Elicitation -1
ThetasksetsforRequirementsgatheringactionforasimpleproject
mayinclude:
1.Makealistofstakeholdersfortheproject.
2.Inviteallstakeholderstoaninformalmeeting.
3.Askeachstakeholdertomakealistoffeaturesandfunctions
required.
4.Discussrequirementsandbuildafinallist.
5.Prioritizerequirements.
6.Noteareasofuncertainty.
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11. Example of a Task Set for Elicitation -2
ThetasksetsforRequirementsgatheringactionforabigprojectmay
include:
1.Makealistofstakeholdersfortheproject.
2.Intervieweachstakeholdersseparatelytodetermineoverallwantsand
needs.
3.Buildapreliminarylistoffunctionsandfeaturesbasedonstakeholder
input.
4.Scheduleaseriesoffacilitatedapplicationspecificationmeetings.
5.Conductmeetings.
6.Produceinformaluserscenariosaspartofeachmeeting.
7.Refineuserscenariosbasedonstakeholderfeedback.
8.Buildarevisedlistofstakeholderrequirements.
9.Usequalityfunctiondeploymenttechniquestoprioritizerequirements.
10.Packagerequirementssothattheycanbedeliveredincrementally.
11.Noteconstraintsandrestrictionsthatwillbeplacedonthesystem.
12.Discussmethodsforvalidatingthesystem. 11

12. How to decide?
–Bothapproachesinthepreviousslidesdothesameworkwith
differentdepthandformality.
–Choosethetasksetsthatachievethegoalandstillmaintainquality
andagility.
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13. Process Patterns
•Aprocesspattern
–describesaprocess-relatedproblemthatisencounteredduring
softwareengineeringwork,
–identifiestheenvironmentinwhichtheproblemhasbeen
encountered,and
–suggestsoneormoreprovensolutionstotheproblem.
•Statedinmoregeneralterms,aprocesspatternprovidesyouwitha
template[Amb98]—aconsistentmethodfordescribingproblem
solutionswithinthecontextofthesoftwareprocess.
(definedatdifferentlevelsofabstraction)
1.Problemsandsolutionsassociatedwithacompleteprocessmodel
(e.g.prototyping).
2.Problemsandsolutionsassociatedwithaframeworkactivity(e.g.
planning)or
3.anactionwithaframeworkactivity(e.g.projectestimating).
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14. Process Pattern Types
•Stagepatterns—definesaproblemassociatedwithaframeworkactivity
fortheprocess.Itincludesmultipletaskpatternsaswell.Forexample,
EstablishingCommunicationwouldincorporatethetaskpattern
RequirementsGatheringandothers.
•Taskpatterns—definesaproblemassociatedwithasoftware
engineeringworktaskandrelevanttosuccessfulsoftwareengineering
practice
•Phasepatterns—definesthesequenceofframeworkactivitiesthatoccur
withtheprocess,evenwhentheoverallflowofactivitiesisiterativein
nature.ExampleincludesSprialModelorPrototyping.
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15. An Example of Process Pattern
•Describesanapproachthatmaybeapplicablewhenstakeholdershaveageneralideaof
whatmustbedonebutareunsureofspecificsoftwarerequirements.
Patternname.RequirementsUnclear
Intent.Thispatterndescribesanapproachforbuildingamodelthatcanbeassessed
iterativelybystakeholdersinanefforttoidentifyorsolidifysoftwarerequirements.
Type.Phasepattern(associatedwithCommunicationPhase)
Initialcontext.Conditionsmustbemet(1)stakeholdershavebeenidentified;(2)amodeof
communicationbetweenstakeholdersandthesoftwareteamhasbeenestablished;(3)the
overridingsoftwareproblemtobesolvedhasbeenidentifiedbystakeholders;(4)an
initialunderstandingofprojectscope,basicbusinessrequirementsandproject
constraintshavebeendeveloped.
Problem.Requirementsarehazyornonexistent.stakeholdersareunsureofwhattheywant.
Solution.Adescriptionoftheprototypingprocesswouldbepresentedhere.
Resultingcontext.Asoftwareprototypethatidentifiesbasicrequirements(modesof
interaction,computationalfeatures,processingfunctions)isapprovedbystakeholders.
Followingthis,1.Thisprototypemayevolvethroughaseriesofincrementstobecome
theproductionsoftwareor2.theprototypemaybediscarded.
Relatedpatterns.CustomerCommunication,IterativeDesign,IterativeDevelopment,
CustomerAssessment,RequirementExtraction.
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16. Process Assessment and Improvement
SPcannotguaranteethatsoftwarewillbedeliveredontime,meettheneeds,or
hasthedesiredtechnicalcharacteristics.
However,theprocesscanbeassessedtoensurethatitmeetsasetofbasic
processcriteriathathavebeenshowntobeessentialforasuccessfulsoftware
engineering.
StandardCMMIAssessmentMethodforProcessImprovement(SCAMPI)—
providesafivestepprocessassessmentmodelthatincorporatesfivephases:
initiating,diagnosing,establishing,actingandlearning.
CMM-BasedAppraisalforInternalProcessImprovement(CBAIPI)—
providesadiagnostictechniqueforassessingtherelativematurityofasoftware
organization;usestheSEICMMasthebasisfortheassessment[Dun01]
SPICE—TheSPICE(ISO/IEC15504)standarddefinesasetofrequirementsfor
softwareprocessassessment.Theintentofthestandardistoassistorganizationsin
developinganobjectiveevaluationoftheefficacyofanydefinedsoftwareprocess.
[ISO08]
ISO9001:2000forSoftware—agenericstandardthatappliestoanyorganization
thatwantstoimprovetheoverallqualityoftheproducts,systems,orservicesthatit
provides.Therefore,thestandardisdirectlyapplicabletosoftwareorganizationsand
companies.[Ant06]
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17. PROCESS MODELS
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18. PRESCRIPIVE PROCESS MODELS
The waterfall model
the V-model
Incremental process model
Evolutionary model
prototyping
the spiral model
Concurrent model
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19. Prescriptive Process Models
•Originallyproposedtobringordertochaos.
•Prescriptiveprocessmodelsadvocateanorderlyapproachtosoftware
engineering.
–However,willsomeextentofchaos(lessrigid)bebeneficialtobring
somecreativity?
Thatleadstoafewquestions…
•Ifprescriptiveprocessmodelsstriveforstructureandorder(prescribea
setofprocesselementsandprocessflow),aretheyinappropriatefora
softwareworldthatthrivesonchange?
•Yet,ifwerejecttraditionalprocessmodels(andtheordertheyimply)and
replacethemwithsomethinglessstructured,dowemakeitimpossibleto
achievecoordinationandcoherenceinsoftwarework?
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20. The Waterfall Model
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ItistheoldestparadigmforSE.Whenrequirementsarewelldefinedand
reasonablystable,itleadstoalinearfashion.
(problems:1.rarelylinear,iterationneeded.2.hardtostateallrequirements
explicitly.Blockingstate.3.codewillnotbereleaseduntilverylate.)
Theclassiclifecyclesuggestsasystematic,sequentialapproachtosoftware
development.

21. The V-Model
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Avariationofwaterfallmodel
depictstherelationshipofquality
assuranceactionstotheactions
associatedwithcommunication,
modelingandearlycodeconstruction
activates.
Teamfirstmovesdowntheleftside
oftheVtorefinetheproblem
requirements.Oncecodeis
generated,theteammovesupthe
rightsideoftheV,performinga
seriesofteststhatvalidateeachof
themodelscreatedastheteam
moveddowntheleftside.

22. The Incremental Model
•Wheninitialrequirementsarereasonablywelldefined,buttheoverall
scopeofthedevelopmenteffortprecludesapurelylinearprocess.
–Acompellingneedtoexpandalimitedsetofnewfunctionstoalater
systemrelease.
•Itcombineselementsoflinearandparallelprocessflows.
–Eachlinearsequenceproducesdeliverableincrementsofthesoftware.
•Thefirstincrementisoftenacoreproductwithmanysupplementary
features.
–Usersuseitandevaluateitwithmoremodificationstobettermeetthe
needs.
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23. The Incremental Model
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24. Evolutionary Models
Softwaresystemevolvesovertimeasrequirementsoftenchangeas
developmentproceeds.Thus,astraightlinetoacompleteendproduct
isnotpossible.However,alimitedversionmustbedeliveredtomeet
competitivepressure.
Usuallyasetofcoreproductorsystemrequirementsiswell
understood,butthedetailsandextensionhaveyettobedefined.
Youneedaprocessmodelthathasbeenexplicitlydesignedto
accommodateaproductthatevolvedovertime.
Itisiterativethatenablesyoutodevelopincreasinglymorecomplete
versionofthesoftware.
Twotypesareintroduced,namelyPrototypingandSpiralmodels.
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25. Evolutionary Models: Prototyping
•Whentouse:Customerdefinesasetofgeneralobjectivesbutdoesnotidentify
detailedrequirementsforfunctionsandfeatures.OrDevelopermaybeunsure
oftheefficiencyofanalgorithm,theformthathumancomputerinteraction
shouldtake.
•Whatstep:Beginswithcommunicationbymeetingwithstakeholderstodefine
theobjective,identifywhateverrequirementsareknown,outlineareaswhere
furtherdefinitionismandatory.Aquickplanforprototypingandmodeling
(quickdesign)occur.Quickdesignfocusesonarepresentationofthoseaspects
thesoftwarethatwillbevisibletoendusers(interfaceandoutput).Design
leadstotheconstructionofaprototypewhichwillbedeployedandevaluated.
Stakeholder’scommentswillbeusedtorefinerequirements.
•Bothstakeholdersandsoftwareengineersliketheprototypingparadigm.Users
getafeelfortheactualsystem,anddevelopersgettobuildsomething
immediately.However,engineersmaymakecompromisesinordertogeta
prototypeworkingquickly.Theless-than-idealchoicemaybeadoptedforever
afteryougetusedtoit.
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26. Evolutionary Models: Prototyping
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Construction
of prototype
communication
Quick
plan
Modeling
Quick design
Construction
of prototype
Deployment
delivery &
feedback

27. Evolutionary Models: The Spiral
Itcouplestheiterativenatureofprototypingwiththecontrolledandsystematicaspects
ofthewaterfallmodelandisarisk-drivenprocessmodelgeneratorthatisusedtoguide
multi-stakeholderconcurrentengineeringofsoftwareintensivesystems.
Twomaindistinguishingfeatures:oneiscyclicapproachforincrementallygrowinga
system’sdegreeofdefinitionandimplementationwhiledecreasingitsdegreeofrisk.
Theotherisasetofanchorpointmilestonesforensuringstakeholdercommitmentto
feasibleandmutuallysatisfactorysystemsolutions.
Aseriesofevolutionaryreleasesaredelivered.Duringtheearlyiterations,therelease
mightbeamodelorprototype.Duringlateriterations,increasinglymorecomplete
versionoftheengineeredsystemareproduced.
Thefirstcircuitintheclockwisedirectionmightresultintheproductspecification;
subsequentpassesaroundthespiralmightbeusedtodevelopaprototypeandthen
progressivelymoresophisticatedversionsofthesoftware.Eachpassresultsin
adjustmentstotheprojectplan.Costandscheduleareadjustedbasedonfeedback.Also,
thenumberofiterationswillbeadjustedbyprojectmanager.
Goodtodeveloplarge-scalesystemassoftwareevolvesastheprocessprogressesand
riskshouldbeunderstoodandproperlyreactedto.Prototypingisusedtoreducerisk.
However,itmaybedifficulttoconvincecustomersthatitiscontrollableasitdemands
considerableriskassessmentexpertise.
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28. Evolutionary Models: The Spiral
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29. Three Concerns on Evolutionary Processes
•Firstconcernisthatprototypingposesaproblemtoprojectplanning
becauseoftheuncertainnumberofcyclesrequiredtoconstructtheproduct.
•Second,itdoesnotestablishthemaximumspeedoftheevolution.Ifthe
evolutionoccurstoofast,withoutaperiodofrelaxation,itiscertainthatthe
processwillfallintochaos.Ontheotherhandifthespeedistooslowthen
productivitycouldbeaffected.
•Third,softwareprocessesshouldbefocusedonflexibilityandextensibility
ratherthanonhighquality.Weshouldprioritizethespeedofthe
developmentoverzerodefects.Extendingthedevelopmentinordertoreach
highqualitycouldresultinalatedeliveryoftheproductwhenthe
opportunitynichehasdisappeared.
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30. Concurrent Model
Allowasoftwareteamtorepresentiterativeandconcurrentelementsofanyof
theprocessmodels.Forexample,themodelingactivitydefinedforthespiral
modelisaccomplishedbyinvokingoneormoreofthefollowingactions:
prototyping,analysisanddesign.
TheFigureshowsmodelingmaybeinanyoneofthestatesatanygiventime.
Forexample,communicationactivityhascompleteditsfirstiterationandinthe
awaitingchangesstate(notshown).Themodelingactivitywasininactive
state,nowmakesatransitionintotheunderdevelopmentstate.Ifcustomer
indicateschangesinrequirements,themodelingactivitymovesfromtheunder
developmentstateintotheawaitingchangesstate.
Concurrentmodelingisapplicabletoalltypesofsoftwaredevelopmentand
providesanaccuratepictureofthecurrentstateofaproject.Ratherthan
confiningsoftwareengineeringactivities,actionsandtaskstoasequenceof
events,itdefinesaprocessnetwork.
Eachactivity,actionortaskonthenetworkexistssimultaneouslywith
otheractivities,actionsortasks.Eventsgeneratedatonepointtrigger
transitionsamongthestates.
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31. Concurrent Model
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32. Specialized Process Models
Componentbaseddevelopment—theprocesstoapplywhenreuseisa
developmentobjective(likespiralmodel)
Formalmethods—emphasizesthemathematicalspecificationofrequirements(
easytodiscoverandeliminateambiguity,incompletenessandinconsistency)
AspectOrientedsoftwaredevelopment(AOSD)—providesaprocessand
methodologicalapproachfordefining,specifying,designing,andconstructing
aspects
UnifiedProcess—a“use-casedriven,architecture-centric,iterativeand
incremental”softwareprocesscloselyalignedwiththeUnifiedModeling
Language(UML)tomodelanddevelopobject-orientedsystemiterativelyand
incrementally.
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33. The Unified Process (UP)
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inception
elaboration