System Dynamics Applications / 1 / 1.5 / 1.5.1

1.5.1 Qualitative Models

We can build models that are qualitative or quantitative in nature. Each type of model has particular purpose and utility. Generally, qualitative models are developed to formalise conceptual views of stakeholders in the problem under investigation. Formalisation usually involves creating diagrammatic representations such as causal diagrams. These are specific statements of dynamic hypotheses we need to formulate along the journey of enhancing our understanding of such problems.

Dynamic hypotheses are sets of statements and representations of the causes and how these produce changes over time. These are evaluated through iterative processes involving building and testing systems dynamics models and comparing their behaviour and the behaviour we expect to see in the real world.

The purpose of any model we create is to provide an experimental framework for testing our dynamic hypotheses and new managerial policies and strategies we might be considering for subsequent implementation. In system dynamics modelling, a policy is management action applied at a single point to create desired modification of systemic behaviour (Coyle, 1996). Strategy usually involves the employment of policies in combination. Every model must be built with the aim of enhancing our understanding of complex problems that we cannot fully understand without having a model to help us.