Subject: Systems Thinking

Posted by Marcus J Williams on 9/1/2006
In Reply To:Systems Thinking Posted by Philip Abode on 8/31/2006

Message:

Philip,

I found your question interesting:

> By definition, a system comprising two or more parts working together
> to accomplish common purpose, Is it not?

My answer would be it depends on where you draw your system's boundaries, and for that matter, how you define the common purpose. Many of the systems models that I see don't satisfy your proposed definition. Some examples:

- Take an air-conditioning system. One could say that its common purpose is to achieve and maintain a given environmental temperature. If you wanted to model the aircon system and chose to exclude the environment to be conditioned from your system model (and have the temperature input to the thermostat be exogenous), then yes, the air-conditioning system and the parts that comprise it all work together to accomplish the common purpose - maintaining a given temperature. However, if you included the environment in your model it doesn't follow that the environment, now a part of the system, is a willing party to the common purpose. If the environment is small room and you have a window aircon unit, then it may comply. Open the door, the environment is suddenly the whole atmosphere and you may never get to the desired temperature. In other words, the environment doesn't care about the aircon's purpose - it has its own independent properties.

- The aircon example may seem silly, but here's another example. The firm I work with has built a long-term national-scale transportation energy and emissions model for Canada. It represents things such as the human population (which generates transportation demand), the stock of road vehicles, fuel sources, etc. One might say the common purpose of a national transportation system is the provision of ample and sustainable transportation service to the population. As I mentioned, the population is part of our system model, and if immigration and population growth occur (which is expected for Canada) then the population part of the system is not chipping in to meet the common purpose, it's actually creating more transportation demand (unless one simulates a significant modal shift to rickshaws, which we don't!).

It is worth noting that the type of systems modelling and simulation that we practice - the Design Approach to Socio-Economic Modelling - differs somewhat from traditional systems dynamics, especially in the treatment of feedbacks. But at the end of the day a system is a system. My point is that many systems contain elements that are not working towards some common or desired purpose, and in many cases a systems model is constructed to learn how to better control systems containing elements which are at odds with some desired outcome.

Hope this perspective is useful.

Marcus J. Williams

Follow Ups:

Systems Thinking - Joe Rimback 9/4/2006 
Systems Thinking - Bill Braun 9/1/2006