System dynamics

Introduction

System dynamics refers to a type of computer modeling and computer simulation created in the 1960s by Dr. Jay W. Forrester of the Massachusetts Institute of Technology. It originally was used in management and engineering, but is now used to model all sorts of simpler or complex systems. A well know example is the Club of Rome model Wrold3 model (wikipedia) developed for the limits to growth report by Meadows et al. .

In the field of system dynamics, a system is defined as a collection of elements that continually interact over time to form a unified whole. The underlying relationships and connections between the components of a system is called the structure of the system. One familiar example of a system is an ecosystem. The structure of an ecosystem is defined by the interactions between animal populations, birth and death rates, quantities of food, and other variables specific to a particular ecosystem. The structure of the ecosystem includes the variables important in influencing the system.

The term dynamics refers to change over time. If something is dynamic, it is constantly changing. A dynamic system is therefore a system in which the variables interact to stimulate changes over time. System dynamics is a methodology used to understand how systems change over time. The way in which the elements or variables composing a system vary over time is referred to as the behavior of the system. In the ecosystem example, the behavior is described by the dynamics of population growth and decline. The behavior is due to the influences of food supply, predators, and environment, which are all elements of the system.

(The First Step, retrieved Feb 2019)

Software

• Simantics, Open operating system for modelling and simulation. It comes with a System dynamics tool. See Tutorial: Basic System Dynamics Modelling and Tutorial: Advanced System Dynamics Modelling.
• Stella, probably the most popular commercial system used in education.
• iThink
• Simile from Simulistics. A commercial software.
• Vensim® Personal Learning Edition (free for personal and educational use)

Links

MIT System dynamics tutorials

A number of open courseware materials can be found, e.g.

• System Dynamics II (2013)
• System Dynamics Self Study (1998/99). This class is organised trough nine roadmaps which in turn include various readings and exercises. See Syllabus and Readings

Example PDFs

• The First Step
• Modeling ExercisesSection 1

Other

• System dynamics (Wikipedia). Includes a nice adopter model.

• Modelling predator-prey interaction from Simulistics. See also their other tutorials

For folks with math skills

• Dynamical system (Wikipedia)
• Lotka–Volterra equations (Wikipedia)