Object-oriented qualitative simulation of human mental models of complex systems

A qualitative model of an expert´s mental model of a complex system (advanced nuclear power plant) was developed from the qualitative physics of confluences and simulated using an object-oriented extension to Common LISP (Flavors). Invisible connections for flow compatibility, control connections, iterative propagation, and embedded propagation were among the features provided for derivation of causal ordering. Deterministic output was guaranteed through stochastic state transition. Using a fictitious loop fragment showed changes in flow rate change through a pump. State transition models provided excellent fits to the simulation data and showed that all conditions converged to steady state. Strictly forward (with the flow) propagation facilitated consistency within intermediate pre-equilibrium states and convergence as compared to forward propagation with limited backward propagation. The psychological plausibility of qualitative simulation models was evaluated. A further extension of mythical causality is suggested, for which constraint propagation executes on multiple levels of aggregation