
Fuzzy Sets, Fuzzy Operators, and Fuzzy Relations 159
Remark 2.19 We could require a different Property 4, for example, h (a, 0) = a and
h (0, b) = p, in which case h is a t-conorm. We nd such a requirement for h is much
less plausible than Property 4, hence we recommend h as a t-norm.
Remark 2.20 The Extension Principle can claim that (2.130) is exactly what is
achieved by applying the existing formula for the union of two type-2 fuzzy sets to to
and , and it is correct (when h is a t-norm). However, we obtain (2.130) without
applying Extension Principle.
Now we stipulate the following result,
Theorem 2.5 [183] The union of two type-2 fuzzy ...