3.2 Using Degree of Sufficiency and Necessity (PROSPECTOR)

PROSPECTOR [5] can be considered another successful expert system. In PROSPECTOR the uncertainty associated with a rule is described by two values (LS and LN) which express the degree of sufficiency and necessity with which the conditional part of a rule (E) implies the conclusion (H):

(5)

If we define the prior and posterior odds on H given E respectively as

(6)

we obtain the following definition

(7)

The formula used in PROSPECTOR for rule combination is as follows :

(8)

where

This approach also assumes conditional independence on all Ei 's.