esd.36j system & project management...author cc_cmehta created date 2/15/2005 10:20:02 am

ESD.36J System & Project Management

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Copyright © 2003James M. Lyneis

Dynamics of Project Performance

System Dynamics and Project Management

Class Two (9/25/03)

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Topics

• Dynamic project problems and the system dynamics viewpoint

• The dynamics of project performance -- the rework cycle

• The dynamics of project performance --feedback effects

• Practice for 9/30

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Topics





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Examples of Behavior Modes on a Project

ProjectStaffing

Time

TypicalPlan

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Examples (continued)

FractionComplete

Time

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1

TypicalPlan

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Examples (continued)

Productivity(Normalised)

Time

1

2Typical

Plan

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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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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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System Dynamics Tools

“Soft” tools --behaviour-over-time graphscausal-loop diagrammingsystem archetypesmental simulation

“Systems Thinking”

“Hard” tools --computer modelscomputer simulationcalibration to datasensitivity and what-if analyses

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Causal loop diagrams -- causal linksAn arrow with a positive sign (+) or an “s” means that, all else remaining equal, an increase (decrease) in the first variable increases (decreases) the second variable above (below) what it would otherwise have been.

BankBalance

InterestEarned+

s

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Causal loop diagrams -- causal linksAn arrow with a positive sign (+) or an “s” means that, all else remaining equal, an increase (decrease) in the first variable increases (decreases) the second variable above (below) what it would otherwise have been.

An arrow with a negative sign (-) or an “o” means that, all else remaining equal, an increase (decrease) in the first variable decreases (increases) the second variable below (above) what it otherwise would have been.

BankBalance

InterestEarned+

s

Price Orders-o

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Exercise -- link and loop polarity

InventoryProduction Shipments

OrderedBooksSalesforce Price

PopulationBirths Deaths

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Causal loop diagrams -- loop polarity

Reinforcing loops -- loops with all positive or an even number of negative causal linksBalancing loops -- loops with an odd number of negative causal links

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Reinforcing or Balancing?Attractiveness

of Market

Profits

IndustryPrice

Number ofCompetitors

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Reinforcing or Balancing?

Unit Cost ofProduction

CumulativeProduction

Price

Demand

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The “dominant” loop on a project may be a controlling loop ...

Staff

Progress+

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Desired Progress

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Time

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With “reinforcing” loops complicating that control ...

Staff

Progress+

Desired Progress

Experience

Productivity

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With “reinforcing” loops complicating that control ...

Staff

Progress+

Desired Progress

Experience

Productivity

Overtime

Fatigue

Delay

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Time delayed actionTime delayed action Non-linear responsesNon-linear responses

Cause-effect relationshipsCause-effect relationshipsExperience Productivity

New Staff Productivity

Time

Productivity

Years of experience

The main elements within feedback loops are...

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As the final element of system structure, there are two kinds of variables ...

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/Jatia 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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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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Emphasis on Internal Dynamics

System-as-cause thinkingWhat can we do to improve our performance and accomplish our objectives ...Proactive and offensive

Vs.System-as-effect thinking

Others did it to usPredictive, reactive, defensive

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Topics





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What are typical stocks & flows on a project?

Stocks Flows

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The Traditional View of a Program

WORKBEING DONE

PEOPLE PRODUCTIVITY

WORKTO BEDONE

WORKDONE

WORK TO DO STAFF % DONE

TIMETIMETIME

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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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Definitions

Productivity --Work accomplished per hour of effort,

regardless of completeness or correctnessQuality --Fraction of work just accomplished that is

correct and complete, i.e. will not need rework.

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But traditional approaches fail to consider rework

WORKBEING DONE

PEOPLE PRODUCTIVITY QUALITY

WORKTO BEDONE

WORKREALLYDONE

REWORK


RWK

TIME TIME TIME

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Or Undiscovered Rework

WORK

BEING DONE

PEOPLE PRODUCTIVITY QUALITY

KNOWNREWORK

UNDISCOVEREDREWORK

REWORK DISCOVERY

WORKTO BEDONE

WORKREALLYDONE


RWK

UR REALLY

TIME TIME TIME

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Rework shows up as revisions to work products

Virtually all complex projects have revisions cycles

REV 0

REV 1

REV 3...

REV 2

Accomplishment of Revisionsto Design Products (e.g., Drawings)

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

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

Simulated Original Plan Actual

Disguised results from actual vehicle project

… 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

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

Original Work Rework

Disguised results from actual vehicle project

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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Perceived vs. Actual Progress: SRS DevelopmentPerceived Actual100.

75.

50.

25.

0.

TIME1/93 1/94 1/95 1/96 1/97 1/98 1/99 1/00 1/01 1/02

c:\mydocu~1\jml\hughes\hisjml.dyn 8/19/97 9:29

Disguised resultsfrom actual aerospace project

Year 1 Year2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 10Year 9

Or Two Years !!

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and the “90% Syndrome” ---Design Progress (Percent Complete)

Simulated100.

75.

50.

25.

0.

TIME1/85 1/89 1/91 1/93 1/95 1/97 1/99 1/01

Disguised resultsfrom actual aerospace project

Year 1 Year2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8

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The rework cycle concept was originally developed by Pugh-Roberts Associates, but is now common ...

Originally called the “Work Accomplishment Structure” [see Cooper, Kenneth G., “Naval Ship Production: A Claim Settled and a Framework Built,” Interfaces, Vol. 10, No. 6, December 1980]

Examples from other models --Smith, Bradley J., Nguyen, Nghia, and Vidale, Richard F., “Death of a Software Manager: How to Avoid Career Suicide Through Dynamic Software Process Modeling,” American Programmer, Vol.6, No. 5, May 1993.Homer, et. al. “Delivery Time Reduction in Pulp and Paper Mill Construction Projects: A Dynamic Analysis of Alternatives,” Proceedings of the 1993 International System Dynamics Conference.Abdel-Hamid, Tarek K. and Madnick, Stuart E., Software Project Dynamics: An Integrated Approach, Prentice-Hall, Englewood Cliffs, NJ, 1991.

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Topics





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On a Typical Project, Productivity & Quality Vary Over Time

Why??

Productivity(Normalised)

Time

1

2Typical

Plan

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Productivity: AC DesignEquiv. Drawings/Person-Year10.

7.5

5.

2.5

0.

TIMEc:\mydocu~1\jml\b2\b2jml.dyn 8/18/97 13:08

Why??

Yr 1 Yr 2 Yr 3 Yr 4 Yr 5 Yr 6 Yr 7 Yr 8 Yr 9 Yr 10 Yr 11

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Why??

Quality (%): AC DesignQuality Average Quality to Date100.

75.

50.

25.

0.

TIMEc:\mydocu~1\jml\b2\b2jml.dyn 8/18/97 13:08

Yr 1 Yr 2 Yr 3 Yr 4 Yr 5 Yr 6 Yr 7 Yr 8 Yr 9 Yr 10 Yr 11

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Benchmarking Data -- Average ‘Quality’

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

Defense

Commercial

100%

MIN AVG MAX

0.68

0.34

AVGMIN MAX

[From a survey of 21 software development projects (14 commercial, 7 defense, 6 companies); Cooper, K.G. and T. W. Mullen. 1993. Swords and Plowshares: The Rework Cycles of Defense and Commercial Software Development Projects American Programmer, May edition.]

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Why ?? -- Drivers of Dynamics

The “rework cycle”Feedback effects on productivity and work quality

Positive, reinforcing, often “vicious circles”Negative, controlling

Knock-on effects between work phases

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What drives productivity & quality?

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Progress

ReworkDiscovery

Productivity Quality

Work ToBe Done

UndiscoveredRework

KnownRework

WorkReally Done

Develop a causal diagram for the effects ...

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Work Qualityto Date

ScheduledCompletion

Time

ExpectedCompletion

TimeAvailability

of Prerequisites

PerceivedProgress

SchedulePressure

Out-of-SequenceWork

Morale

ExpectedHours at

Completion

Hours Expended

to Date

Skill &Experience

Hiring

EquivalentStaff onProject

StaffingRequested

Progress

ReworkDiscovery

TurnoverOrganisationalSize

Changes

Staff


AddedWork Obsoleted

Work

Overtime

TimeRemaining

Work ToBe Done

UndiscoveredRework

KnownRework

WorkReally Done

Project Dynamics

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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 -- Dynamics of Project Performance

The “rework cycle”QualityUndiscovered rework

Feedback effects on productivity and work quality

Positive, re-enforcing, often “vicious circles”Negative, controlling

Knock-on effects between work phases

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Work Qualityto Date

ScheduledCompletion

Time

ExpectedCompletion

TimeAvailability

of Prerequisites

PerceivedProgress

SchedulePressure

Out-of-SequenceWork

Morale

ExpectedHours at

Completion

Hours Expended

to Date

Skill &Experience

Hiring

EquivalentStaff onProject

StaffingRequested

Progress

ReworkDiscovery

TurnoverOrganisationalSize

Changes

Staff


AddedWork Obsoleted

Work

Overtime

TimeRemaining

Work ToBe Done

UndiscoveredRework

KnownRework

WorkReally Done

Management Actions ??

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Lessons

Rework is the most important single factor driving schedule and budget overruns

Project problems can quickly “snowball”

“Soft Factors” such as overtime and morale can be big drivers of rework

Management actions are a key part of the feedback loops

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Hard tools force us to be more explicit, and accurately simulate the consequences of our models ...

“Soft” tools --behaviour-over-time graphscausal-loop diagrammingsystem archetypesmental simulation

“Hard” tools --computer modelscomputer simulationcalibration to datasensitivity and what-if analyses

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Topics





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Practice for 9/30

1. Building from the Class1 Step 3 model (or your own version if desired), complete the equations for the rework cycle model as illustrated in the following diagram.

2. Assume that staff, productivity, quality, and rework discovery time are constants. A VENSIM diagram of the model, plus some hints, follows. Assume that there are 100 tasks to be done; set the normal values for productivity, quality, and rework discovery time at 1 task/month/person, 1.0, and 4 months, respectively.

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Practice for 9/30 (cont.)

2. Simulate the model, and verify that the results match the Class1 Step3 model.

3. Now set normal quality to 0.75, and simulate the model. When does the project finish? What happens to undiscovered rework?

4. Which has a greater impact on the project, a 33% increase in quality (from the 0.75 base) or a 33% increase in productivity?

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Work to Do Work DoneUndiscoveredRework

Work Accomplishment

Rework Generation

Rework Discovery

Quality

StaffProductivity

Potential WorkRate

Time to Discover Rework

Project FinishedSwitch

CumulativeWork Done

Rate of Doing Work

<Rework Generation>

<Work Accomplishment>

Feasible WorkRate

Maximum WorkRate

Minimum Time toPerform a Task

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If the world consists only of stocks and flows, what are those other variables indicated on the diagrams??

“Auxillaries” -- components of ratesConstants (e.g., factors which may be stocks or flows, but which do not change over the time span of the simulation)External inputs

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Example of an Auxillary

The Rate:Work Accomplishment = Feasible Work Rate

* QualityThe Auxillaries:

Feasible Work Rate = Min(Maximum Work Rate, Potential Work Rate)Potential Work Rate = Staff Level *

Productivity * Project Finished SwitchThe Constant: Quality = .75

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Hints

Representing a delay:Rework Discovery = Undiscovered Rework / Time to Discover Rework[This equation produces a delay between the

time when rework is created and when it is discovered; in steady state, the delay time equals Time to Discover Rework. We will look at delays in more detail later.]

esd.36j system & project management...author cc_cmehta created date 2/15/2005 10:20:02 am

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