Uncertainty affects decision-making and emerges in a number
of different forms. The concept of information is inherently associated
with the concept of uncertainty. The most fundamental aspect
of this connection is that the uncertainty involved in any problem solving
situation is a result of some information deficiency, which
may be incomplete, imprecise , fragmentary , not fully reliable, vague,
contradictory, or deficient in some other way. Uncertainty is
an attribute of information. The general framework of fuzzy reasoning
allows handling much of this uncertainty and fuzzy systems
employ type-1 fuzzy sets, which represent uncertainty by numbers
in the range [0, 1]. When an entity is uncertain, like a measurement,
it is difficult to determine its exact value, and of course
type-1 fuzzy sets make more sense than sets. However, it is not
reasonable to use an accurate membership function for something
uncertain, so in this case what we need is another type of fuzzy
sets, those which are able to handle these uncertainties, the so
called type-2 fuzzy sets (Karnik and Mendel, 1998). The amount
of uncertainty in a system can be reduced by using type-2 fuzzy logic
because this logic offers better capabilities to handle linguistic
uncertainties by modeling vagueness and unreliability of information