Reasoning Under Uncertainty

Please read it and send me comments, objections, etc. 1) Victor [Yu] has assigned certainty factors to his rules based on the relative strengths of the evidence in these rules. While trying to find a numerical scale that would work as he wanted it to with the system's 0.2 cutoff and combining functions, he had to adjust certainty factors of various rules. Now that this scale has been established, however, he assigns certainty factors using this scale, and does NOT adjust certainty factors of rules if he doesn't like the system's performance. Furthermore, he does NO combinatorial analysis before determining what CF to use; he is satisfied that using the scale he has devised, the system's combining function, and the 0.2 cutoff, the program will arrive at the right results for any combination of factors, and if it doesn't, he looks for missing information to add. 2) Assuming that the parameters IDENT and COVERFOR are disambiguated in Victor's set of rules, Ted [Shortliffe] believes the CF's that Victor uses in his rules, and approves of the idea of using a cutoff for COVERFOR since this is what we've been doing with bacteremia (since it is a binary decision, a cutoff makes sense for COVERFOR). Furthermore, this is quite similar to what clinicians do: they accumulate lots of small bits of clinical evidence, then decide if the total is enough to make them cover [or a particular organism--independent of what the microbiological evidence suggests.