Extreme Programming Extreme Programming and Systems and Systems EngineeringEngineering

Similarities and Similarities and SynergySynergy

(based on talk given to INCOSE New England Chapter)(based on talk given to INCOSE New England Chapter)

Joseph (Yossi) WeihsJoseph (Yossi) WeihsSept 10Sept 10thth, ,

20042004

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AbstractAbstract

XP is one of the popular ‘Agile’ XP is one of the popular ‘Agile’ software development disciplinessoftware development disciplines

Systems engineers may have to deal Systems engineers may have to deal with software teams practicing XPwith software teams practicing XP

What should you look out for, and What should you look out for, and what can you exploit when working what can you exploit when working with an XP oriented team?with an XP oriented team?

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ContentsContents

Overview – what is XPOverview – what is XP Why use XPWhy use XP Overlap with SEOverlap with SE Key differencesKey differences Integrated methodsIntegrated methods Summary / Take HomeSummary / Take Home

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Agile MethodsAgile Methods

Formality - from lightweight to Formality - from lightweight to ‘heavy’:‘heavy’:

ScrumScrum

XPXP

Crystal OrangeCrystal Orange

DSDMDSDM

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OverviewOverview

Extreme Programming is a Extreme Programming is a software development software development methodology that originated methodology that originated about seven years agoabout seven years ago

XP is winning recognition in large XP is winning recognition in large organizationsorganizations

XP is bunched together with Lean XP is bunched together with Lean development and Agile processesdevelopment and Agile processes

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Must have a flow chartMust have a flow chart

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History of XPHistory of XP

Started out as a Started out as a one man’s quest one man’s quest Kent BeckKent Beck

Defined four Defined four values in 1996:values in 1996:– CommunicationCommunication– SimplicitySimplicity– FeedbackFeedback– Courage Courage

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History of XP History of XP (continued)(continued) Since 1999 it has been publicly Since 1999 it has been publicly

evangelized. Numerous publications evangelized. Numerous publications have sprung uphave sprung up

2004 – XP is in use in many 2004 – XP is in use in many organizations, large and smallorganizations, large and small

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Why XP?Why XP?

The approach works best when:The approach works best when: Project has numerous requirement Project has numerous requirement

changeschanges High risk developmentHigh risk development Applied to small (30<) teamsApplied to small (30<) teams Testability is a requirement (V&V!)Testability is a requirement (V&V!)

Use XP only with whole software team buy-Use XP only with whole software team buy-in!in!

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XP Cost of ChangeXP Cost of Change

Cost of change

0

Ana

lysi

s

Des

ign

Cod

ing

Mai

nten

ance

Development phase

Traditional Development

eXtreme Programming

Steve Hayes (steve@khatovartech.com)

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XP and RiskXP and Risk

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Core XP PrinciplesCore XP Principles

Incremental changeIncremental change Assume simplicityAssume simplicity Rapid feedbackRapid feedback Embracing the changeEmbracing the change Quality workQuality work

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Core XP PracticesCore XP Practices

Broken down to four domains:Broken down to four domains:

PlanningPlanning DesigningDesigning

CodingCoding TestingTesting

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PlanningPlanning

– User storiesUser stories– Release planning / release planRelease planning / release plan– Make frequent small releasesMake frequent small releases– Project velocityProject velocity– Iterative developmentIterative development– Iteration planningIteration planning– Move people aroundMove people around– Daily stand up meetingDaily stand up meeting– Fix XP when it breaksFix XP when it breaks

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DesigningDesigning

– Simplicity is the keySimplicity is the key– Choose a system metaphorChoose a system metaphor– CRC cardsCRC cards– Spike solutionSpike solution– Never add functionality earlyNever add functionality early– Re-factor mercilesslyRe-factor mercilessly– YAGNI = You Ain’t Gonna Need ItYAGNI = You Ain’t Gonna Need It

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CodingCoding

– On site customerOn site customer– Coding standardCoding standard– Code unit then testCode unit then test– Pair programmingPair programming– Sequential integrationSequential integration– Integrate oftenIntegrate often– Collective code ownershipCollective code ownership– Optimize lastOptimize last– 40 hours a week40 hours a week

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TestingTesting

– Unit testsUnit tests– When a bug is found…When a bug is found…– Acceptance testsAcceptance tests

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XP Life CycleXP Life Cycle

Exploration phaseExploration phase Planning phasePlanning phase Iterations to releaseIterations to release ProductionizingProductionizing Death phaseDeath phase

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XP Team MembersXP Team Members

ProgrammersProgrammers CustomersCustomers TestersTesters TrackersTrackers CoachCoach ConsultantsConsultants ManagerManager

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XP roles an SE playsXP roles an SE plays

CustomerCustomer – the SE is requirements – the SE is requirements advocate and validation testeradvocate and validation tester

TrackerTracker – SE may act as project – SE may act as project manager, including risk mitigationmanager, including risk mitigation

Tester Tester – SE may facilitate some tests– SE may facilitate some tests Coach Coach – SE’s as discipline leader– SE’s as discipline leader Manager Manager – SE as boss in large project– SE as boss in large project

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XP & SE – OverlapXP & SE – Overlap

XPXP Systems EngineeringSystems EngineeringPlanningPlanning Development plan, risk Development plan, risk

managementmanagement

TestingTesting Validation & verificationValidation & verification

CoachCoach Systems engineerSystems engineer

CollectivCollective e ownershiownershipp

System integrationSystem integration

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XP Iterations and SEXP Iterations and SE

XP: Assume XP: Assume customer does not customer does not

have clear have clear definition of system definition of system

at any pointat any point

SE: Maximize SE: Maximize planning, scenario planning, scenario

building risk building risk assessment before assessment before

starting workstarting work

Collision? Sometimes, but SE can still manage process: trickle feed XP’rs requirements disguised as customer stories, according to SE requirement rankings

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XP Customer and SEXP Customer and SE

XP: Customer Rep XP: Customer Rep available at all available at all

times for iterations:times for iterations:

Requirements, Requirements, risks, priorities, risks, priorities,

validationvalidation

SE: Customer signs SE: Customer signs off on SOW, gets off on SOW, gets

briefed on progress briefed on progress and accepts and accepts product at product at milestonesmilestones

Collision? Sometimes – when working with XP teams, use their power throughout project initiation, and transition more structured disciplines as project matures

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Additional XP & SE Additional XP & SE issuesissues XP’s short iterations and local XP’s short iterations and local

focus fit concept exploration focus fit concept exploration phasephase

XP is the least formalistic of the XP is the least formalistic of the Agile methods : On-Site CustomerAgile methods : On-Site Customer

Pair Programming can cause Pair Programming can cause cultural problemscultural problems

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Integrated ApproachesIntegrated Approaches

Small XP teams within larger Small XP teams within larger projectsprojects

Software – part heavyweight, part Software – part heavyweight, part XPXP

Extreme / Agile Project Extreme / Agile Project ManagementManagement

Extreme applied to other Extreme applied to other engineering disciplinesengineering disciplines

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Summary / Take HomeSummary / Take Home

Works well for smaller software Works well for smaller software projects / proof of conceptprojects / proof of concept

Works with CMMI / UML (to a point)Works with CMMI / UML (to a point) No fixed cookbook – tailor it to your No fixed cookbook – tailor it to your

projectproject Spill over to project management Spill over to project management

and general engineering and general engineering managementmanagement

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ReferencesReferences

Extreme Programming Explained, Extreme Programming Explained, Kent Beck, Addison Wesley 1999Kent Beck, Addison Wesley 1999

Re-factoring: Improving the Re-factoring: Improving the Design of Existing Code, Martin Design of Existing Code, Martin Fowler, Addison Wesley 1999 Fowler, Addison Wesley 1999

Many web sitesMany web sites

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LinksLinks

http://www.http://www.extremeprogrammingextremeprogramming.org.org http://www.xp2001.orghttp://www.xp2001.org http://www.iturls.com/English/SoftwareEnginehttp://www.iturls.com/English/SoftwareEngine

ering/xpm_apm.aspering/xpm_apm.asp http://www.balagan.org.uk/work/http://www.balagan.org.uk/work/ http://collaboration.csc.ncsu.edu/laurie/Paperhttp://collaboration.csc.ncsu.edu/laurie/Paper

s/XPSardinia.PDFs/XPSardinia.PDF http://www.xprogramming.com/http://www.xprogramming.com/ http://www.dsmweb.org/http://www.dsmweb.org/ http://www.martinfowler.com/articles/http://www.martinfowler.com/articles/

newMethodology.htmlnewMethodology.html

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Extra SlidesExtra Slides

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XP - The Four Core XP - The Four Core ValuesValues

Communication.Communication. Simplicity.Simplicity. Feedback.Feedback. Courage.Courage.

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CommunicationCommunication

Often problem that arise in SW project can Often problem that arise in SW project can be tracked back to lack of communication.be tracked back to lack of communication.

XP enforces the XP enforces the Communication ValueCommunication Value by by employing many employing many practicepractice that could not be that could not be carried without communicating (e.g. pair carried without communicating (e.g. pair programming, unit testing etc.).programming, unit testing etc.).

XP employs a XP employs a CoachCoach whose job is that of whose job is that of noticing when people are notnoticing when people are not communicating and reintroduce communicating and reintroduce them.them.

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SimplicitySimplicity

XP embrace the principle of “Make it XP embrace the principle of “Make it Simple”Simple”

XP is betting that it is better to do a XP is betting that it is better to do a simple thing today and pay a little more simple thing today and pay a little more tomorrow to change it, if it needs to be tomorrow to change it, if it needs to be changed, than building a more complicate changed, than building a more complicate system that has feature that will never be system that has feature that will never be used.used.

Simplicity and Communication support Simplicity and Communication support each other mutually.each other mutually.

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FeedbackFeedback

Feedback works in XP at different time Feedback works in XP at different time scales.scales.

Programmers have feedback on a Programmers have feedback on a minutes time scale on the status of the minutes time scale on the status of the system thanks to unit tests.system thanks to unit tests.

When customers write new When customers write new stories stories the the programmers estimate those programmers estimate those immediately to give prompt feedback to immediately to give prompt feedback to the customer about the quality of the the customer about the quality of the stories.stories.

The customer review the scheduler The customer review the scheduler every 2-3 weeks and provide prompt every 2-3 weeks and provide prompt feedback to the developer.feedback to the developer.

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CourageCourage

XP team should have the courage of XP team should have the courage of throwing code away.throwing code away.

XP team should have the courage of XP team should have the courage of mainly refactor the architecture of the mainly refactor the architecture of the system, if architectural flaw are system, if architectural flaw are detected.detected.

Courage has in XP the same role that Courage has in XP the same role that mutation has in genetic algorithms. mutation has in genetic algorithms. Takes you out of local Takes you out of local maximum/minimum.maximum/minimum.