Subject: Education for Sustainability Standard

Posted by Richard Turnock on 11/6/2011
In Reply To:Education for Sustainability Standard Posted by Jaimie Cloud on 11/6/2011

Message:

Question 2 revised:

The phrase “problems and their solutions are endogenous”

In the process of building a model of a system (using systems thinking tools or dynamic modeling software), the modeler must define the boundaries of the system. Within the boundaries of the system, the problems, solutions, feedback, flows and accumulations are endogenous. Outside the system boundary everything is exogenous. The modeler moves the boundaries of the system as they revise, update, improve, add more complexity, add feedback loops, add flows and add accumulations.

The modeling technique I was always taught is to start small and then expand the boundaries after going through a complete verification and validation cycle to compare with the real world. Expanding the boundaries to include more flows and accumulations increases the complexity but also creates opportunities for consensus and more long lasting impacts of changes. Expanding the system boundaries to include all the stakeholders helps resolve problems.

Only within the system boundary will there be a standard procedure to have a complete process for model development, verification and validation. When an exogenous thing (problem or solution) is proposed then the modeler has to start over with a new system boundary and complete the model development, verification and validation for the new flows and accumulations.


Richard Turnock
email: richardturnock@comcast.net