Troubleshooting

   The Relation of Troubleshooting to Envisioning

   The task of troubleshooting is, in many ways, the inverse of envisioning. The troubleshooter needs to move from known function to unknown structure, whereas the envisioning moves from known structure to unknown function. If a fault has in some way perturbed the structure of the device, the troubleshooter, even though he may have complete access to the behavior of the faulted device, no longer has total information about its structure (because, for example, a fault that opened a diode's junction might not, of course, be directly observable). The troubleshooter asks the question, "What could have caused this (symptomatic) overall behavior?" rather than, "What behavior do all these local component behaviors produce when connected in this way?" This troubleshooting process, like that of envisioning, entails extensive problem solving in order to resolve ambiguities. For the troubleshooter, the ambiguities lie in determining which of the many possible causes for a given symptom is the actual one. (deKleer & Brown, 1983, p. 181)