Axiomatic theory of intuitionistic fuzzy sets (Q1971950)

The first attempt for an axiomatization of the theory of intuitionistic fuzzy sets (IFSs) [see \textit{K. Atanassov}, ibid. 20, 87--96 (1986; Zbl 0631.03040)] is made. The axioms are related to the IFSs, to the relations over them, and to the modal-type operators (\(\square\) and \(\lozenge\)) defined over them. The present account determines the direction of future research related to the axiomatization of the topological operators, to the extended modal operators and to the level operators defined over the IFSs.