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System dynamics’ iterative modeling process

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System dynamics’ iterative modeling process

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  1. 1 . P r o b l e m A r t i c u l a t i o n ( B o u n d a r y S e l e c t i o n ) 5 . P o l i c y 2 . D y n a m i c F o r m u l a t i o n H y p o t h e s i s & E v a l u a t i o n 4 . T e s t i n g 3 . F o r m u l a t i o n System dynamics’ iterative modeling process Monitoring and Evaluation Figure 3-1 Results of any step can yield insights that lead to revisions in any earlier step (indicated by the links in the center of the diagram). From Chapter 3, pages 83 – 105 in Sterman, John (2000) Business Dynamics: Systems Thinking and Modeling for a Complex World. Irwin McGraw-Hill

  2. Systems Thinking • Everyone agrees that “systems thinking” includes these. - Some people say system thinking encompasses these too, Policy design is best with the aid of simulation, but, in the absence of simulation, is certainly better with the endogenous systems thinking view than without. The Modeling Process “Systems Thinking”vs. “System Dynamics” • 1) Problem articulation • Theme selection • Key variables • Time horizon • Dynamic problem definition (reference modes) • 2) Formulation of dynamic hypothesis • Initial hypothesis generation • Endogenous focus • Mapping (CLDs, SFDs, HDs) • 3) Formulation of a simulation model • Specification • Estimation • Tests • 4) Testing • Comparison to reference modes • Robustness under extreme conditions • Sensitivity • Many other tests… (see chap 21) • 5) Policy design and evaluation • Scenario specification • Policy design • “What if…” analysis. • Sensitivity analysis • Interactions of policies perspectiveand a set of conceptual tools rigorous modeling method [Chapter 3 of Sterman (2000)]

  3. Ford Modeling Process • Ford process on page 13 and pages 149-152 • Compare to previous two slides • My opinion • Both very similar, I tend to Sterman’sbecause fewer steps. • Draw dynamic hypothesis first as CLD or SFD, whichever seems to lend itself better to the problem. Mix and match. It’s just a sketch! • I like having a step for equations (Ford implicitly includes this in his Step 3) • Other modeling processes (not covered - similar – I can send info) • Eberlein (Vensim documentation) • Saeed • Richardson • Etc.

  4. Reference Modes • Drawn (explicit) in book • Mono Basin p47-51 • Kaibab Plateau p267-272 • Written (implicit) in book • epidemics p87 • Boomtown p104-105 & p307-308 • homeostasis p117-118 • Salmon p189-191 • Feebatesp209-212 • Real Estate p245-247 • Pred/prey p255-256 • DDT p289-292(esp.292) • Electric Power p308-309 Draw one in PowerPoint Groups for homework 1: 1, 4 & 7 2: 2, 5 & 8 3: 3, 6 & 9

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