Reference: Karp, P. D. & Friedland, P. Coordinating the Use of Qualitative and Quantitative Knowledge in Declarative Device Modeling. January 1988, 1988.
Abstract: We describe several new qualitative representation and reasoning techniques. These techniques allow us to represent both state variables and the interactions between them with varying degrees of precision. This is desirable when we have only partial knowledge about these entities, or when we wish to express approximations to the knowledge we do have. New reasoning strategies have been developed to allow the propagation of different types of values through the different types of interactions to simulate the behavior of a device.