
Fuzzy Logic 283
The answer provided by the extension principle may be expressed as the inference
rule:
X is A
is
where the membership function of is dened by:
(3.56)
subject to the condition
, .
In particular, if the function is 1:1, then Equation (3.56) simplies to:
where is the inverse of v.
Example 3.50
and
.
As in the case of the entailment rule, the dispositional version of the extension
principle has the simple form:
Remark 3.18 The dispositional extension principle plays an important role in in-
ference from commonsense knowledge.