qualitative system dynamics model

describing a system is, in itself, a useful thing to do which might lead to better understanding of the problem in question

– Qualitative and quantitative modelling in system dynamics

Apparently there's some debate between the relative merits of qualitative system dynamics models vs quantitative system dynamics models.

Using SD qualitatively involves focusing on discovering the feedback loops to describe a dynamically complex system. In this case, the use of tools such as causal loop diagrams (CLD) (see table 1 for an explanation), and in some occasions stocks and flow networks [stock and flow diagrams], without quantitative modeling is enough to provide insights for decision makers (Lane and Husemann 2008; Kunc and Morecroft 2009)

– System dynamics: a soft and hard approach to modelling