SQsim: A Simulator for Imprecise ODE Models

This article describes a method for representing and simulating Ordinary Di erential Equation (ODE) systems which are imprecise { that is, where the ODE model contains both parametric and functional uncertainty. Such models, while useful in engineering tasks such as design and hazard analysis, are not used in practice because they require either special structures which limit the describable uncertainty or produce predictions which are extremely weak. This article describes SQsim (for SemiQuantitative SIMulator), a system which provides a general language for representing and reasoning about many common forms of engineering uncertainty. By de ning the model both qualitatively and quantitatively and This work has taken place in the Qualitative Reasoning Group at the Arti cial Intelligence Laboratory, The University of Texas at Austin. Research of the Qualitative Reasoning Group is supported in part by NSF grants IRI-9216584 and IRI-9504138, by NASA grants NCC 2-760 and NAG 2-994, and by the Texas Advanced Research Program under grant no. 003658-242. yPlease address all correspondence to Professor Benjamin Kuipers, Computer Science Department, University of Texas at Austin, Austin, Texas 78712 USA. Please see the Note at the end of the paper. by using a simulation method that combines inferences across the qualitative-to-quantitative spectrum, SQsim produces predictions that maintain a precision consistent with the model imprecision.