Where are type-2 fuzzy sets being used?
They are being used in type-2 fuzzy logic systems, and they let us model uncertainties totally within the framework of fuzzy logic. See the fourth and fifth articles in this collection titled “Frequently Asked Questions About Rule-Based Type-2 Fuzzy Logic Systems” and “Applications for Rule-Based Type-2 Fuzzy Logic Systems” for a description about these FLSs.