All major approaches to Qualitative Reasoning rely on the existence of a model of the physical system. However, the task of finding a model is usually far from trivial. Within the area of electrical engineering, model building methods have been developed to automatically deduce models from measurements. In this paper we explicitly show how to incorporate qualitative knowledge in order to apply these methods to situations where they do not behave satisfac torily. A program has been developed and

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... ap plied to a non-trivial example. The qualitative input, in terms of an incomplete bond graph, and the resulting output can be used to form a more complete bond graph. This more infor mative model is suitable for further reasoning.