Generating explanations of pathophysiological system behaviors from qualitative simulation of compartmental models

This paper describes a method for generating, in a language that is comprehensible by the user, explanations of the behaviors of a pathophysiological system from compartmental models. Such behaviors are obtained through the qualitative simulation of a model of the pathophysiological system, which has been built within the QCMP (Qualitative Compartmental Modeling Framework) framework and directly coded into the QSIM language. The main advantage offered by this explanation facility over the simulation outcome plots consists in its capability of explaining how and why the predicted behavior arises from the structure of the modeled system and physical laws. The basic idea underlying the explanation algorithm consists in determining a causal concatenation of the changes from a state to its successor: the algorithm when comparing two successive states will single out those changes that are a direct consequence of the direction of change in the state and will propagate the effects of these changes following the causal order between variables which is implicitely defined by the compartmental structure.