Invariance and nominal value mapping as key themes for qualitative simulation

The paper discusses the purpose of qualitative studies in simulation modelling and analysis. The notions of invariance (with regards to system structures, input and output) and nominal value mapping are seen as central concepts, or ‘themes,’ to the variety of qualitative methods that currently exist in simulation. Thus the present purpose is to try to help unify the study of qualitative methods by relating them to each other using the key themes. In the work, we have found that many different scientific and engineering disciplines have been doing simulation using qualitative methodology; the present purpose, then, is to illustrate that these efforts are connected and that the collective concepts and methodology can be potentially utilized as a set of interdisciplinary tools. The thrust in qualitative methods is seen as a step to making quantitative methods more accessible and usable by many different types of researchers and project managers. However, as is emphasized in the text, it must be made certain that qualitative approaches are carefully studied so that there is no falling into the trap of using ambiguous input to generate purely ambiguous results; results must, in the long term, be directly useful to decision makers that rely on simulation, among other tools, to make well-informed decisions. The paper also stresses that the choice of which input, output, and model to use depends on the specific goals of the analyst. It is too easy, sometimes, either to create qualitative solutions that have no utility, or to make qualitative an expression that has a more powerful quantitative equivalent.