CFRL: A Language for Specifying the Causal Functionality of Engineered Devices

Understanding the design of an engineered device requires both knowledge of the general physical principles that determine the behavior of the device and knowledge of what the device is intended to do (i.e., its functional specification). However, the majority of work in model based reasoning about device behavior has focused on modeling a device in terms of general physical principles or intended functionality, but not both. In order to use both functional and behavioral knowledge in understanding a device design, it is crucial that the functional knowledge is represented in such a way that it has a clear interpretation in terms of actual behavior. We propose a new formalism for representing device functions with well-defined semantics in terms of actual behavior. We call the language CFRL (Causal Functional Representation Language). CFRL allows the specification of conditions that a behavior must satisfy, such as occurrence of a temporal sequence of expected events and causal relations among the events and the behavior of device components. We have used CFRL as the basis for a functional verification program which determines whether a behavior achieves an intended function.