At 09:51 PM 5/7/96 -0700, Timothy C. May wrote:

In particular, one form of belief representation seems especially relevant: Dempster-Shafer theory.

Two quick things: (more in my forthcoming thesis) 1. It is very instructive to consider systems for considering trust and belief (and Dempster-Shafer is a rather nice one). However, these systems (my own decision analysis discussion to a degree, but less so with respect to information gathering) and Dempster-Shafer in particular require the events to be independent: "Further, Dempster-Shafer theory provides rules for combining probabilities and thus for propagating measures through the system. This fourth point is possibly the most attractive, but it is also one of the most controversial since the propagation method is an extension of the multiplication rule for independent events. Since many of the applications involve events that are surely dependent, that rule is, by classical statistical criteria, inapplicable. The tendency to assume that events are independent unless proven otherwise has stimulated a large proportion of the criticism of probability approaches; as it stands, Dempster-Shafer theory suffers the same ill" [Shapiro (ed.) Encyclopedia of Aritificial Intelligence. /Reasoning, Default./ p 846.] The very term "Web of Trust" makes one pause with respect to independent events. 2. Just as a comment, it seems there are different meaning of "transitiviy" in related but different disciplines, for instance in value and utility functions, one requires transitivity, but in a way different from what Hal discusses: "For any three possible set os of consequences, X1, X2, and X3, if X1 > X2 and X2 > X3 then the preference is transitive such that X1 > X3." [deNeufville, R. Applied Systems Analysis: Engineering Planning and Technology Management, 1990, p 313.] This refers to a single person's preferences (rather than 3 individuals in a "network.") _______________________ Regards, Men govern nothing with more difficulty than their tongues, and can moderate their desires more than their words. -Spinoza Joseph Reagle http://farnsworth.mit.edu/~reagle/home.html reagle@mit.edu E0 D5 B2 05 B6 12 DA 65 BE 4D E3 C1 6A 66 25 4E