deweck-dynamics software projects - École Polytechnique

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Copyright 2007Olivier L. de Weck and James M. Lyneis

Dynamics of Software Projects

Prof. Olivier de Weck

[email protected]

Guest Lecture at Ecole Polytechnique

October 5, 2007

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Copyright 2007de Weck and Lyneis

Topics

Dynamic project problems

The system dynamics viewpoint

Causes of project dynamics

Application of System Dynamics to Modeling Small to Medium Size Software Projects

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Topics





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Project Dynamics

What does “dynamic” mean in the context of a project?What are some key measures typically monitored on a project?Sketch “desired” (or planned) and typical actuals for these measures.

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Sketch Plan and Actuals for ...

Time

ProjectStaffing

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FractionComplete

Time

.5

1

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Productivity(Normalised)

Time

1

2

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Trouble-free Projects Behave as Planned: Design Labor (Equivalent People)

Simulated Data100.

75.

50.

25.

0.

TIME91 92 93 94 95 96

Disguised resultsfrom an actualsoftware project

Year 1 Year 5Year 4Year 3Year 2 Year 6

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Design Progress (Percent Complete)Simulated100.

75.

50.

25.

0.

TIMEYear 1 Year 4Year 3Year 2 Year 5 Year 6

Disguised resultsfrom an actual

software project

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Design Labor (Equivalent People)Simulated Data80.

60.

40.

20.

0.

TIME

Disguised results from an actual Ship-building project

Year 1 Year 4Year 3Year 2

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Design Progress (Percent Complete)Simulated100.

75.

50.

25.

0.

TIMEYear 1 Year 4Year 3Year 2

Disguised results from an actual Ship-building project

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So while some projects are trouble-free, more typically, projects ...

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Typical Project “Disasters”

The Channel Tunnel -- original estimate, $3 billion; final cost, $10 billionBoston’s “Big Dig” -- original mid-1980’s estimate, $2.5 billion; latest estimate, $14.5 billion (9/2001)

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Microsoft’s next major release of Windows operating system

January 2003: Longhorn will ship in 2004 http://redmondmag.com/news/article.asp?EditorialsID=5674

August 2004: Will Ship late 2006http://arstechnica.com/news.ars/post/20040828-4139.html

Windows Vista (AKA “Longhorn)

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FBI’s Virtual Case File

Virtual Case File is would allow agents to share info easilyCongress and others believe VCF is “critical to enabling the FBI and intelligence agencies to ‘connect the dots’ in preventing [terrorist] attacks”InformationWeek Feb 4, 2005

May 2004: Project will be delivered by end of 2004 Feb 2005: Mueller acknowledges he doesn’t know how much it will cost ($170 million already spent) or when it will be deliveredFBI may have to scrap what they’ve done so far and start fresh

InformationWeek Feb 4, 2005 from the Associated Press

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Software Projects are Tough

On average software projects overshoot schedule by 50%⅓ of large-scale software projects never complete (cancelled)¾ of all large systems that are completed are operating failures*

Source: Gibbs, W. 1994. “Software’s Chronic Crisis”. Scientific American. September. pp. 86-95

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Lamri Survey

http://www.lamri.com/CMMI_Survey_results.pdf

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So while some projects are trouble-free, more typically, projects ...

... Surprise us with late requests for additional time or resources... Have schedule and budget overruns... Seem to get stuck at “90%” complete... Result in new products with flaws discovered after release... Hinder learning because of difficulty in comparing the performance of different, “unique” projects

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On typical development projects ...Design Labor (Equivalent People)

Simulated Actual

Year

800.

600.

400.

200.

0 0 3 6 9 12 15 18 21

ApproximateOriginal Plan

Disguised results from actual aerospace project

… Staffing experiences an extended tail

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Program Staff, Simulated vs. Data (Equivalent Staff)

400.

300.

200.

100.

TIME

0 Year 1 Year 2 Year 3 Year 4 Year 5 Year 6

Simulated Original Plan Actual

Disguised results from actual vehicle project

… Or a second staffing peak

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Two software development projects for the same aerospace company experienced dramatically different results

[see next 3 pages; figures show disguised results shifted so that the 2 projects started in the same year]

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1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

150

100

50

0

Program staff (Program A ...)

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1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

150

100

50

0

Program staff (Program B)

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1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

150

100

50

0

Program staff (Program B vs. Program A)

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What caused the differences between Program A and Program B?

Differences in work scope?

External Conditions?

Management policies and processes?

And how can a company learn from these differences, and therefore

Bid better?

Plan better?

Manage better?

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Progress has been made: Many firms have cut development times in half ...

Source: Smith, Preston G. and Donald G Reinersten, Developing Products in Half the Time (2nd edition), Wiley 1998.

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PERT and CPM (Critical Path Method)Waterfall, Spiral, …Emphasis on “soft,” people factorsMicrosoft Project

.. and Learning is not happeningWhy???

Project problems persist in spite of numerous advances in the last 30 years

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Topics





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Events “Change Occurred,Project behind schedule”

Three ways of looking at a problem --

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Events

Patterns of

BehaviorEst. CompletionDate

Add.Resources

“Project behind schedule”


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System Structure

EstimatedCompletion

Date

AddResources

BehindSchedule

RemainingWork

Experience Dilution,Quality Problems


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Events

Patterns of Behavior

System Structure

Est. CompletionDate

Add.Resources

EstimatedCompletion

AddResources

BehindSchedule

RemainingWork

Experience Dilution,Quality Problems

“Project behind schedule”


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The System Dynamics Viewpoint

Events


System Structure

External Factors

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The System Dynamics Viewpoint

Events


System Structure

Low

Medium

High

Ability toInfluence

External Factors

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Why??

Project performance problems are fundamentally dynamic problems,

but Managers mental models and typical tools (computer models):

Attribute all problems to external factorsView a project statically (no iteration, no feedback)Treat projects as if they were unique

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System Dynamics Concepts

Focus on dynamic behaviorSystem structure as cause of that behaviorEmphasis on internal dynamics and how we can change structureA model is an integral part of organizational learning

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Examples of Behavior Modes

"Plan"

Growth

ProjectStaffing

Stability

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What Causes Dynamics?

All dynamics are driven by –Feedback processesAccumulation processes

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The basic element of system structure is the feedback loop...

Chickens

TIME

...This one a “positive,”or reinforcing feedback loop.

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EGGS CHICKENS

Adapted from Professor John Sterman, MIT

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Loops of effects interact with one another, making traditional diagnosis quite difficult...

...Such as with this “negative,” or balancing, feedback loop, which may

slow or reverse growth

Chickens

TIME

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EGGS CHICKENS ROADCROSSINGSX

FARMSIZE

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Effects interacting makes traditional diagnosis quite difficult in a business setting as well

PRICE

UNITCOSTS

USAGE

SERVICECAPACITY

SERVICEQUALITY

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Accumulation processes involve ...

Stocks or “levels” -- define the state of the system

Flows or “rates” -- define the rate of change in system states

Bank Account Balance

Deposits

(iThink Rate Symbol)

Deposits

(Vensim/DYNAMO Symbol)

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Connecting stocks and flows ...

Bank Account Balance

Deposits Withdrawals

“Clouds”represent stocks outside the system boundary

StaffHiring Firing

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Interacting positive and negative feedback loops of cause-effect relationships, with stocks, flows, delays, and non-linearities, are capable of generating all observed modes of behavior.

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Topics





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System dynamics modeling provides a means of ...

... understanding the structure of projects, and how that structure creates behavior;... designing robust projects... learning across projects

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But every project is unique ...

Many similarities, some uniquenessWe will discuss the characteristics of different kinds

of projects later in the term.

SD is a framework for assessing dynamic similaritiesBut, there is no “one way”, “right answer”We will discuss heuristics and rules of thumb during

the course.

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Examples of Behavior Modes on a Project

ProjectStaffing

Time

TypicalPlan

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Examples (continued)

FractionComplete

Time

.5

1

TypicalPlan

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Examples (continued)

Productivity(Normalised)

Time

1

2Typical

Plan

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The Drivers of Project Dynamics --

The “rework cycle”Feedback effects on productivity and work quality (often “vicious circles”)Knock-on effects between work phasesKnock-on effects between projects

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What are typical stocks & flows on a project?

Stocks Flows

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The Traditional View of a Program – Task Accomplishment

WORKBEING DONE

PEOPLE PRODUCTIVITY

WORKTO BEDONE

WORKDONE

WORK TO DO STAFF % DONE

TIMETIMETIME

Task Accomplishment

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The traditional view, expanded to multiple tasks with logical links ...

... becomes a Critical Path Network

Task A

Task B

Task C

Task D

Task E

Task F Task Z

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But traditional approaches fail to consider iteration and rework

WORKBEING DONE

PEOPLE PRODUCTIVITY QUALITY

WORKTO BEDONE

WORKREALLYDONE

REWORK


RWK

TIME TIME TIME

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Or Undiscovered Rework

WORKBEING DONE

PEOPLE PRODUCTIVITY QUALITY

KNOWNREWORK

UNDISCOVEREDREWORK

REWORK DISCOVERY

WORKTO BEDONE

WORKREALLYDONE


RWK

UR REALLY

TIME TIME TIME

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On typical development projects ...Simulated Actual

Year

800.

600.

400.

200.

0 0 3 6 9 12 15 18 21

ApproximateOriginal Plan

Disguised results from actual aerospace project

… Staffing experiences an extended tail

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Caused by the need to accomplish rework

0 3 6 9 12 15 18 21

800.

600.

400.

200.

0

Work Assignments of Staff to...

Original Work

Rework

Total

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Program Staff, Simulated vs. Data (Equivalent Staff)

400.

300.

200.

100.

TIME


Simulated Original Plan Actual


… A second staffing peak

On typical development projects ...

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Work Assignments of Staff to...

Again caused by the need to execute rework

400.

300.

200.

100.

TIME


Original Work Rework


Rework

Original Work

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The Rework CycleKey to Project Dynamics

WORK

BEING DONE

People Productivity Quality

Rework Discovery

WORKTO BEDONE

KNOWNREWORK

UNDISCOVEREDREWORK

WORKREALLYDONE

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Why? The Drivers of Project Dynamics --


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What drives productivity & quality?

UndiscoveredRework

KnownRework

WorkReally Done

WorkTo Be Done

Progress

Rework Discovery


CustomerChanges

Dynamics are initiated by (1) an infeasible initial plan, or (2) changes adding scope and obsoletingcompleted work ...

Scope Growth

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UndiscoveredRework

KnownRework

WorkReally Done

WorkTo Be Done

Progress

Rework Discovery


ApparentProgress

CustomerChanges Schedule

Acceleration

Overtime

Hiring

Scope Growth

… that initiate corrective actions to get the project back

on track...

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UndiscoveredRework

KnownRework

WorkReally Done

WorkTo Be Done

Progress

Rework Discovery


ApparentProgress

CustomerChanges Schedule

Acceleration

Out-of-SequenceWork, Worksite

Congestion, CoordinationProblems,

Morale Problems

AverageEmployee Skill

and Quality

Fatigue,Burnout

Overtime

Hiring

Scope Growth

… that create vicious circles that undercut intended effects

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A system dynamics model usually represents several phases of work, but is more aggregate than a CPM model

SystemEngineering

Software Codeand Test

HardwareDesign

Hardware Buildand Test

Integrateand Test

SoftwareDesign

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Summary: The Drivers of Project Dynamics --


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Topics





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SM Thesis

A Comparative Study of Iterative Prototyping vs. Waterfall Process Applied To Small and Medium Sized Software Projects

Eduardo Malaga ChocanoMIT System Design and Management ProgramJune 2004

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Objectives

1. Identify the main strengths and weaknesses of iterative cycle based models vs. sequential-based models applied to small and medium sized software projects.

2. Measure the impact these features have in the management of projects

3. Understand under which conditions each of these approaches is recommended.

4. Study the new trends in this field and propose recommendations regarding their use.

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Waterfall Projects

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Spiral Projects

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Interviews of Peruvian SW Project Leaders

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Characteristics of Successful Projects

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Source of Problems

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Software Project Model (overview)

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Software Project Model (detailed)

Model Parameters

-Number of Tasks-Development Rate-Verification Rate-Flag

-sequential-iterative

-Verification Period-Phase Size Table-Insight per Phase-Insight Development-Verification Accuracy-% dedicated to verify

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Results (I) – Speed vs Quality

Speed vs QualityRun with nominal parameters

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Results (2) – Task Distribution

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Results (II) – Amount of Rework

Iterative Approach causes more relative rework

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Conclusioniterative

iterative

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SummarySoftware Development Methodology have a significant impact on project success

Iterative Approach:more effective use of developer’s timeshort iterations, minimize idle time waiting for tasks to be reworked

Sequential Approach:programmers wait idle while testing is underwayless rework necessary if insight can be developed fastless variance of outcome

Hybrid Approaches existFinal Note – large difference between software for business applications and safety-critical real-time embedded software

business software – very suitable to spiral approachreal time embedded software – rather sequential

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