  Several different uncertain inference systems (UISs) have been developed for
representing uncertainty in rule-based expert systems. Some of these, such as
Mycin's Certainty Factors, Prospector, and Bayes' Networks were designed as
approximations to probability, and others, such as Fuzzy Set Theory and
DempsterShafer Belief Functions were not. How different are these UISs in
practice, and does it matter which you use? When combining and propagating
uncertain information, each UIS must, at least by implication, make certain
assumptions about correlations not explicily specified. The maximum entropy
principle with minimum cross-entropy updating, provides a way of making
assumptions about the missing specification that minimizes the additional
information assumed, and thus offers a standard against which the other UISs
can be compared. We describe a framework for the experimental comparison of the
performance of different UISs, and provide some illustrative results.
