On the importance of interval sets in type-2 fuzzy logic systems

Type-2 fuzzy logic systems (FLSs) allow uncertainties that occur in rule-based FLSs to be modeled using the new third dimension of type-2 fuzzy sets. Although a complete theory of type-2 FLSs exists for general type-2 fuzzy sets, it is only for interval type-2 fuzzy sets that type-2 FLSs are practical. This paper explains why this is so.