Simulation Modeling (Stock-Flow Translation + Learning-Not-Answers Discipline)

R — Reading

"Every variable can be classified as either a stock or a flow." — Dennis Sherwood, Chapter 12

"Most business objectives — and certainly all the most important ones — can be expressed as the optimization of a portfolio of stocks. The only actions that a manager can take are to readjust the flows." — Dennis Sherwood, Chapter 12

"Models can be used for two main purposes — to get answers, or to gain understanding. ... System dynamics models do not promise such precision. ... It is not about answers — it is all about learning." — Dennis Sherwood, Chapter 13

"Exponential growth masquerading as linear!" — Dennis Sherwood, Chapter 12

I — Interpretation

A CLD shows which variables influence which but does not distinguish state-variables from rates-of-change. Two disciplines complete the bridge from qualitative loop diagram to defensible quantitative reasoning: (1) stock-flow translation — the mechanical craft of classifying every variable, sorting flows by direction, mapping levers to flows, and drawing a simulation-ready plumbing diagram; (2) learning-not-answers — the use-of-model discipline that prevents the resulting simulation from being read as a forecast.