Qualitative, causal reasoning about device behavior

The methods of causal ordering provide an operational means to determine the causal relations among the variables in a model of the equilibrium behavior of a device. The author extends the method to dynamic models as well as mixed models of equilibrium and dynamic equations. He defines self-containment for dynamic and mixed structures and describes causal ordering in such structures. For correct application of the method of causal ordering, the equations comprising the model of a device must be such that each of them comes from an understanding of a conceptually distinct mechanism. To ensure that an equation model satisfies this requirement, an explicit representation of the understanding of mechanisms underlying an equation model was developed. Equations are generated automatically from this representation. An example involving the mixed model of an evaporator is used to illustrate the proposed approach.<>