top of page

System Dynamics Glossary

This is the System Dynamics Glossary compiled by David N. Ford and Accepted by Yaman Barlas. It was published on November 7th 2019 here: https://doi.org/10.1002/sdr.1641.

​

Introduction

As a narrowly focused dictionary, this glossary defines commonly used terms that are central to traditional system dynamics and some more general terms that have special meanings or particular importance within system dynamics. General terms that have no special meanings in system dynamics, application‐specific terms, and software‐specific terms are not included. The reader is referred to the relevant literature for those definitions, as well as detailed descriptions, explanations, and examples of the terms included here.

​

Click on the Concept to View the complete Description.

Concept
Description
Loop dominance
A characteristic of feedback systems in which a loop is strong enough to determine the behavior mode of a part of the system. In a system with multiple loops, the mathematical relations, magnitudes and algebraic signs of variables determine what kind of behavior is dominant in any time period.
Loop polarity
See feedback loop polarity.
Material delay
A continuous delay that captures the time delay in the flow of conserved material through a process.
Mental model
A relatively enduring and accessible, but limited, internal conceptual representation of a system (historical, existing, or projected) whose structure is analogous to the perceived structure of that system. Mental models represent the relationships and assumptions about a system held in a person's mind.
Model boundary
See boundary.
Model credibility (validity)
How well a model represents a given problem; a model's suitability for a particular purpose. A model is credible/valid if it can accomplish what is expected of it, as demonstrated by structure and behavior tests.
Model justification (validation)
The process of developing confidence in a model's credibility and usefulness, performed with tests of model structure similarity to actual structures, simulated behaviors that reflect the behaviors of the system modeled, and ultimately impacts of the model suggestions on actual systems and problems.
Negative feedback
Feedback that works against deviations from a goal. In isolation or if dominant, negative feedback generates goal‐seeking behavior.
Nonlinear relationship
A causal relationship between two variables in which the change in the impacted variable is not directly proportional to the change in the impacting variable.
Open‐loop thinking
Approaching a problem with an exogenous perspective, without applying the importance of feedback (endogenous structure).
Oscillation
Behavior exhibited by a second‐order or a higher‐order system in which the stock value increases and decreases cyclically over time. Three types of oscillation are sustained, where the amplitude stays constant; expanding, where the amplitude increases; and dampened, where the amplitude decreases.
Overshoot and collapse
A behavior mode in which a system variable increases beyond the equilibrium condition, often destroying its ability to sustain itself, and then collapses to lower equilibrium conditions. See growth with overshoot.

References

bottom of page