Dynamic Chatter Abstraction : A scalable technique for avoiding irrelevant distinctions during qualitative simulation

One of the major factors hindering the use of qualitative simulation techniques to reason about the behavior of complex dynamical systems is intractable branching due to a phenomenon called chatter. Chatter occurs when a variable's direction of change is constrained only by continuity within a region of the state space . This results in intractable, potentially infinite branching within the behavioral description due to irrelevant distinctions in the direction of change . Dynamic chatter abstraction provides a general purpose, scalable solution that abstracts chattering regions of the state space into a single state within the behavioral description . Chattering regions are identified via a dynamic analysis of the model and the current qualitative state using knowledge of the inference capability of the simulation algorithm . The algorithm is described along with an empirical evaluation that compares dynamic chatter abstraction to previous solutions and demonstrates that it eliminates all instances of chatter without overabstracting . This technique is used to simulate models that previously could not be simulated . Eliminating the problem of chatter significantly extends the range of problems that can be addressed using qualitative simulation techniques .