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Lecture # 5: Diagrams for Conceptualization, Explanation, and Presentation Four types: Causal-loop diagrams (influence diagrams) Citizen involvement in planning Perception that citizens are powerless and disenfranchised Willingness of citizens to become involved - + - Visitors per year Crowding Natural area Contact area Damage per visitor Incidence of damage Environmental damage Damage density Regeneration time Disappearance of damage R PAD 724 lecture notes Page 28

Lecture # 5: Diagrams for Conceptualization, … · Lecture # 5: Diagrams for Conceptualization, Explanation, and Presentation Four types: Causal-loop diagrams (influence diagrams)

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Lecture # 5: Diagrams for Conceptualization, Explanation, and Presentation

Four types:

Causal-loop diagrams (influence diagrams)

Citizeninvolvement in

planning

Perception thatcitizens are powerlessand disenfranchised

Willingness of citizensto become involved

-+

-

Visitors peryear

Crowding Naturalarea

Contact areaDamage

per visitor

Incidenceof

damageEnvironmental

damage

Damagedensity Regeneration

time

Disappearanceof damage

R

PAD 724 lecture notes Page 28

Averagecommuting time

Averagecommutingdistance

Averagecommuting speed

Tolerablecommuting time

Pressure for more andwider high speed roads

Lane-miles of highspeed roads

Attractivenessof outlying areas

Population inoutlying areas

Number ofcommuters

Net migration tooutlying areas

Highwayconstruction

Far better with loops named in some descriptive, explanatory, or evocative way:

Averagecommuting time

Average commutingdistance

Averagecommuting speed

Tolerablecommuting time

Pressure for moreand wider highspeed roads

Lane-miles of highspeed roads

Attractiveness ofoutlying areas

Population inoutlying areas

Number ofcommuters

Net migrationto outlying

areasHighwayconstruction (B1) Highway

expansion

(B3) Commutingvolume

(B2) Commutingdistance

PAD 724 lecture notes Page 29

Causal loop diagrams with stocks explicit, but flows implicit in the arrows:

Workforce

Net hiring

Progress rate

Cumulative realprogress

Tasks perceivedremaining

Effortperceivedremaining

Indicated worforce

Gross productivity

Initial project definition

Time remainingTime perceived required

Indicated completion date

Scheduledcompletion date

Net additions toschedule

<wcwf>

Undiscoveredrework

Cumulativepreceivedprogress

Fraction satisfactory

Cumulative effort

Perceived productivity

Workforce sought

Willingness tochange

workforceFraction

perceivedcomplete

<Workforce sought>

Detection ofundiscovered

rework

Time to detect rework

<tdrw>

The picture is complete and quantifiable, and may be easier for some audiences to take in because it leaves out the visual complexity of explicit flows as pipes. On the other hand, the fact that the flows are captured as arrows means that the diagram contains less visual information than the same diagram with flows draawn as pipes.

Below is a more complex example of the same idea. Here, pipes would undoubtedly have been too much. The diagram could make sense only as “unfolded,” piece by piece.

PAD 724 lecture notes Page 30

Fund

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rams

Smok

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enes

s of

toba

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health

risk

Pres

sure

on

toba

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keting

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ivities

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keting

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Tax

reve

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from

smok

ers

+

+

+

-

+

Peop

le q

uitt

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smok

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-

Smok

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orm

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ing

smok

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+

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itting

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Rese

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toba

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Pro-

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Ant

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prod

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lity

+

Toba

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grow

ers

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Govt

willingn

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ains

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-+

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Govt

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ding

of

toba

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cont

rol

+

+

Tren

d in t

obac

coco

mpa

ny r

even

ues

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Ant

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<Ant

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PAD 724 lecture notes Page 31

Causal-loop diagrams with explicit stocks and flows (“stock-and-flow/word-and-arrow” diagrams).

This sort of diagram was almost unheard of when Richardson and Pugh proposed it as a “hybrid” diagram (part causal loop diagram, and part “stock-and-flow/feedback” diagram) and suggested it was probably the most appropriate diagram to use for most purposes. Now, of course, it is the standard we experience in Vensim.

New personnel Experiencedpersonnel

AssimilationrateHiring rate

Experiencedleave rate

Time tobecome

experienced

Frac expleaving p year

Total personnel

Target growthrate

Fraction experienced

Mentoring time neededMentoring time available

Mentoring timeneeded per New

Mentoring timeavailable per Exp

Adequacy ofmentoring

Perceived timeto become Exp

Pressure for mentoring

PAD 724 lecture notes Page 32

All of these loop diagrams are improved by naming the loops: see Sterman, p. 748 for another example.

The structure below is a “concept model” used in a group model building effort focusing on problems in the polypropylene/polyethylene industry (essentially a commodity cycle model).

InventoryProducing Shipping

Demand

Productioncapacity

Inventorycoverage

Fraction of orders

shipped

Planned growth incapacity

Capacity inconstruction

Buildingcapacity

Capacityordering

Capacity

acquisition delay

Deliverydelay

Delivery delayperceived by the

market

Phantomordering

Availability loop

Price and capacityadjustment loop

Phantomordering loops

+-

Ordering

Price

The diagram on the next page is a more complex example, with prominent loops named. It comes from a Center for Technology group modeling effort focusing on CTG’s work to facilitate teamwork and information integration in interagency information technology projects.

PAD 724 lecture notes Page 33

Inte

grat

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form

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nU

nint

egra

ted

info

rmat

ion

inte

grat

ing

info

Reso

urce

sal

loca

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toin

tegr

atio

npr

ojec

tad

ding

to

reso

urce

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inte

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ion

Prob

lem

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nera

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inte

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info

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ms

redu

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prob

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Effo

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atin

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fo

Ease

of

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info

Effo

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ore

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ems

Perc

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of in

tegr

ated

info

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Prob

lem

s ge

nera

ted

per

info

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t in

tegr

ated

Will

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to a

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ing

PAD 724 lecture notes Page 34

Sector overview diagramsThese are maps to models, a kind of navigational aid. Be sure to name the links between sectors. Avoid showing too much. See also Sterman, p. 606, for another example.

PAD 724 lecture notes Page 35

Policy structure diagramsSee also Sterman, p. 710, for another example.

PAD 724 lecture notes Page 36

PAD 724 lecture notes Page 37