Managing Occurrence Branching in Qualitative Simulation

Abstract have the simple transition diagram displayed in Figure 1. Qualitative simulators can produce common sense abstractions of complex behaviors given only partial knowledge about a system. One of the problems which limits the applicability of qualitative simulators is the intractable branching of successor states encountered with model of even modest size. Some branches may be unavoidable due to the complex nature of a system. Other branches may be accidental results of the model chosen. Figure 1: Variable transition diagram A common source of intractability is occurrence branching. Occurrence branching occurs when the state transitions of two variables are unordered with respect to each other. This paper extends the QSIM model to distinguish between interesting occurrence branching and uninteresting occurrence branching. A representation, algorithm, and simulator for efficiently handling uninteresting branching is presented. Systems of uncoupled variables First consider the behaviors generated in a system with two uncoupled variables A and B. Let the initial value for both variables is 0 so we can represent the initial state of the sys-tem as the 2-tuple (0,O). Figure 2 displays the transition dia-gram for this system