Interval valued intuitionistic fuzzy sets (Q1121262)

The intuitionistic fuzzy sets (IFS's) of the first author [Fuzzy Sets Syst. 20, 87--96 (1986; Zbl 0631.03040)] are at each point of a given universe of discourse characterized by a pair of degrees: one for membership and the other for non-membership. Here the rather obvious fact first is proven that there is a 1-1 correspondence of such IFS's with interval valued fuzzy sets, a special kind of fuzzy sets of type 2. Later on the IFS's are generalized by allowing the membership as well as the non-membership degrees to be intervals. Fundamental operations are defined and some basic properties proven.