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Introduction to System Dynamics Peter S. Hovmand, PhD, MSW Founding Director, Social System Design Lab Brown School of Social Work Washington University in St. LouisNovember 2011 WUHM Meeting 1
System Dynamics• Field invented by Jay W. Forrester at MIT in 1958• System dynamics: – “The use of informal maps and formal models with computer simulation to uncover and understand endogenous sources of system behavior” [emphasis added] (Richardson, 2011, p. 241)• Foundations of system dynamics: – Endogenous perspective • Stock or level (state) variables representing accumulations – Flow or rate variables representing activity » Using computers to simulate more realistic mathematical modelsRichardson, G.P. (2011). Reflections on the foundations of system dynamics. System Dynamics Review, 27(3), 219‐243.November 2011 WUHM Meeting 2
Model Based System Insights Informal Modeling FormalSurface system insights There is a system Informal The components of a system maps How the components are related through feedback How people might think about a system Where one could intervene Depth What is transformation What is the generic structure What are the implications of accumulations and nonlinear relationships What systems can generate the dynamic behavior Where are the leverage pointsinsightssystem Deep When do boundary conditions determine behavior Why do things happen Simulation models November 2011 WUHM Meeting 3
Examples of different uses of models• Raise awareness and promote learning about complex systems• Motivating discussions about the need to involve multiple stakeholders and solve coordination problems• Policy analysis and design• Motivate changeNovember 2011 WUHM Meeting 4
Todays’ design discussion• Urban Health Model – Overview of the model and interface – Hands‐on experience with using the model and prototype interface• Design discussion – How could you imagine using the model? – Who would you use the model with? – What would need to be developed to facilitate that use? November 2011 WUHM Meeting 5