Evolution of the discontinuity concept in modeling and simulation: from original idea to model switching, switchable understanding, and beyond

The GEneral System Theory implementer (GEST) was the first system-theory-based simulation model specification language. Even though a commercial implementation of GEST was not realized, over the years interesting ideas emerged based on it. At the beginning of this sequence of developments was the realization of two types of discontinuity in the integration of piecewise continuous systems. Afterwards, concepts generalized from the discontinuity processing were applied: (a) to modeling as a model update, multimodels, model switching, DNA-based modeling, dynamic model coupling, and dynamic model composability; (b) to simulations as multisimulation; (c) to psychology as a personality update and dynamic personality in human behavior simulation; (d) to understanding as multiunderstanding, switchable understanding, and misunderstanding avoidance; and (e) to emotion understanding as multiunderstanding and switchable understanding for better emotional intelligence as they are applied to the emotions of self and others. Each one of these areas may be the basis for some advanced modeling and simulation methodologies. Even though references are given for them, the emphasis in this article is the applicability of the same two discontinuity concepts to many different areas.