pam@WHITNEY.STANFORD.EDU (Premla Nangia) (10/24/86)
Speaker: Johan de Kleer
Intelligent Systems Laboratory
Xerox
Palo Alto
Title: Diagnosing Multiple Faults
Time: 4.15 p.m.
Place: Cedar Hall Conference Room
Diagnostic tasks require determining the differences between a
model of an artifact and the artifact itself. The differences between
the manifested behavior of the artifact and the predicted behavior of
the model guide the search for the differences between the artifact and
its model. The diagnostic procedure presented in this paper is
model-based, inferring the behavior of the composite device from
knowledge of the structure and function of the individual components
comprising the device. The system (GDE --- General Diagnostic Engine)
has been implemented and tested on examples in the domain of
troubleshooting digital circuits.
This research makes several novel contributions: First, the system
diagnoses failures due to multiple faults. Second, failure candidates
are represented and manipulated in terms of minimal sets of violated
assumptions, resulting in an efficient diagnostic procedure. Third, the
diagnostic procedure is incremental, exploiting the iterative nature of
diagnosis. Fourth, a clear separation is drawn between diagnosis and
behavior prediction, resulting in a domain (and inference procedure)
independent diagnostic procedure. Fifth, GDE combines model-based
prediction with sequential diagnosis to propose measurements to localize
the faults. The usually required conditional probabilities are computed
from the structure of the device and models of its components. This
capability results from a novel way of incorporating probabilities and
information theory with the context mechanism provided by
Assumption-Based Truth Maintenance.