Jun 01 2008
System Dynamics
System Dynamics is a computer-based simulation modeling methodology developed at the Massachusetts Institute of Technology (MIT) in the 1950s as a tool for managers to analyze complex problems. Its primary audience is still managers, although it has spread widely in academia, where professors and students use it to model systems from every conceivable discipline ranging from history and literature to biology, physics, and economics.
The word “dynamic” implies continuous change and that is what dynamic systems do - they continuously change over time. Their position, or state, is not the same today as it was yesterday and tomorrow it would have changed yet again.
Using System Dynamics simulations allows us to see not just events, but also patterns of behavior over time. The behavior of a system often arises out of the structure of the system itself, and behavior usually changes over time. Sometimes the simulation looks backward, to historical results. At other times it looks forward into the future, to predict possible future results.
Understanding patterns of behavior, instead of focusing on day-to-day events, can offer a radical change in perspective. It shows how a system’s own structure is the cause of its successes and failures. This structure is represented by a series of causally linked relationships. The implication is that decisions made within an organization have consequences, some of which are intentional and some are not. Some of these consequences will be seen immediately while others might not be seen for several years.
System Dynamics simulations are good at communicating not just what might happen, but also why. This is because System Dynamics simulations are designed to correspond to what is, or might be happening, in the real world.
System Dynamics is closely related to systems thinking. System Dynamics was invented to give managers a tool to understand the complex systems that they were charged with controlling. The methodology uses computer simulation models to relate the structure of a system to its behavior over time. Viewed in this way, System Dynamics can translate the understanding gained by systems thinking into a computer simulation model. By experimenting with this prototype of the system at hand, we can gain further knowledge about the system. System Dynamics is capable of creating a learning environment - a laboratory that acts like the system in miniature.
A Quick Overview of the System Dynamics Method
The system dynamics method rests on four fundamental ideas.
The first is that all dynamic behavior in the world occurs when flows are accumulated in levels. A level can be thought of as a bathtub and a flow as a pipe and faucet assembly that fills or drains the tub.
The second fundamental idea is that a system’s levels and flows are embedded in feedback loops. Feedback is the transmission and return of information. In system dynamics modeling, information about a system’s levels travels throughout its structure until it reaches its flows. In response to the information, the flows alter the levels and hence close the feedback loops.
Two kinds of feedback loops exist in system dynamics modeling — positive loops and negative loops. Positive loops generate self-reinforcing behavior and negative loops generate stabilizing or counteracting behavior.
An example of a positive loop is the relationship between births and population in a developing country. As the country’s population increases, its number of births will increase and, as more babies are born each year, its original increase in population is reinforced.
An example of a negative loop is the relationship between deaths and population in a developing country. As the country’s population increases, more of its people will die and, as more people die each year, the country’s original population increase is counteracted or resisted.
The third fundamental idea in system dynamics modeling is that the feedback loops in any system are often joined together by nonlinear couplings. Essentially this means that information about a system’s levels feeds back to affect the levels in nonproportional (and often complicated and unpredictable) ways.
The last fundamental idea in system dynamics modeling is that the dynamic behavior inherent in a system’s interacting web of levels, flows, feedback loops, and nonlinear couplings cannot be ascertained by the unaided human mind, nor solved for mathematically, in closed form. As a result, computer simulation is required to reveal the dynamic behavior of complex systems.
Links:
[System dynamics]
http://en.wikipedia.org/wiki/System_dynamics
- System dynamics is an approach to understanding the behaviour of complex systems over time. It deals with internal feedback loops and time delays that affect the behaviour of the entire system.[1] What makes using system dynamics different from other approaches to studying complex systems is the use of feedback loops and stocks and flows. These elements help describe how even seemingly simple systems display baffling nonlinearity.
[What is System Dynamics?]
http://www.systemdynamics.org/
- System dynamics is a methodology for studying and managing complex feedback systems, such as one finds in business and other social systems. In fact it has been used to address practically every sort of feedback system. While the word system has been applied to all sorts of situations, feedback is the differentiating descriptor here. Feedback refers to the situation of X affecting Y and Y in turn affecting X perhaps through a chain of causes and effects. One cannot study the link between X and Y and, independently, the link between Y and X and predict how the system will behave. Only the study of the whole system as a feedback system will lead to correct results.
- The methodology: 1. identifies a problem, 2. develops a dynamic hypothesis explaining the cause of the problem, 3. builds a computer simulation model of the system at the root of the problem, 4. tests the model to be certain that it reproduces the behavior seen in the real world, 5. devises and tests in the model alternative policies that alleviate the problem, and 6. implements this solution.
[System Dynamics in Education Project]
- System dynamics is a method for studying the world around us. It deals with understanding how complex systems change over time. Internal feedback loops within the structure of the system influence the entire system behavior.
[Road Maps Table of Contents]
http://sysdyn.clexchange.org/road-maps/rm-toc.html
- You can download any chapter of Road Maps in this web
[Software Untuk Simulasi Model System Dynamics]
http://www.lablink.or.id/Sysdyn/Software.htm
- Dynamo, was the first system dynamics simulation language, and for a long time the language and the field were considered synonymous. PowerSim, was later developed as a Windows based environment for the development of system dynamics models that also facilitates packaging as interactive games or learning environments. Vensim, It is an integrated environment for the development and analysis of system dynamics models. IThink / Stella, provided a graphically oriented front end for the development of system dynamics models.
