Abstract: Very rarely do physical devices function as intended by their designers the first time they are implemented. Usually, there are two ways in which the behavior of a device may deviate from the intended one: the device may not exhibit a desired behavior or it may result in an undesirable behavior. We describe a model-based method for solving the latter task. This method involves diagnosis and repair of the failed device and verification of the modified device. It uses compiled structure-behavior- function (SBF) models of how the device works. In an SBF model, the behaviors and the structural elements of a device act as indices into causal mechanisms that explain how the structure of the device produces its behaviors. The causal mechanisms in turn serve as indices into qualitative relations between device variables. The KRITIK2 system uses this indexing scheme to access relevant causal mechanisms and qualitative relations, and uses this knowledge for solving the diagnosis, repair, and verification subtasks of redesign. KRITIK2 shows that this model-based method is sufficient for parametric redesign even for devices in which a single cause results in multiple effects and a single structural element plays a role in multiple causal behaviors. !7
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