System Dynamics Society

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System Dynamics Society

Here a definition, brief description and history of SDS will be placed.

How the Society came to be, a short history given at the 2007 Conference in Boston.

Selected Article

Here will be a description of the main or distinguishing ideas about System Dynamics and Systems Thinking.

Glossary

System Dynamics - short descriptions what System Dynamics is (especially for the non-systemdynamicist;-))

Stock

Levels (stocks) are integrations. The levels integrate (or accumulate) the results of action in a system. The level variables can not change instantaneously. The levels create system continuity between points in time.

Levels (stocks) are changed only by the rates. A level variable is computed by the change, due to rate variables, that alters the previous value of the level. The earlier value of the level is carried forward from the previous period. It is altered by rates that flow over the intervening time interval. The present value of a level variable can be computed without the present or previous values of any other level variables.
(quoted from: Principles of systems, Jay W. Forrester)

1. Stocks characterize the state of the system and provide the basis for actions.
2. Stocks provide systems with inertia and memory.
3. Stocks are the source of delays.
4. Stock decouple rates of flow and create disequilibrium dynamics.
(quoted from: Business Dynamics, pp.195-196, John D. Sterman)