Certainty Factor Combination

If a datum's previous certainty factor is CFp and a new rule computes a certainty factor CFn, the combined certainty factor is given by:

cfcombine(CFp, CFn) =

CFp + CFn * (1 - CFp) CFp > 0, CFn > 0
(CFp + CFn) signs differ
/ (1 - min(| CFp | , | CFn |))
- cfcombine(- CFp, - CFn) CFp < 0, CFn < 0

This algorithm has a desirable feature: it is associative and commutative; therefore the result is independent of the order in which rules are considered.

A CF of + 1 or -1 is dominant and sets the combined CF to that value.

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