Generic Qualitative Behavior of Elementary System Dynamics Structures

The paper starts with some reflections on the qualitative nature of the concepts involved in system dynamics modelling. To deal rigorously with this nature topological tools are needed. These tools are being developed around the qualitative theory of nonlinear dynamical systems. The relevance of this theory to system dynamics is now begining to be understood.The paper introduces a dynamical system associated to the causal diagram that contains only qualitative information. Some interesting results on the qualitative behavior of the system can be obtained from this dynamical system.