“…model, and an F2 framework could be associated to either a B1 or B2 setting. Nevertheless, a commonly-used instance of type-2 fuzziness, interval valued fuzzy sets (IVFS, see [18]), actually devised as B1 objects, has been shown (see [8,9]) to be in certain sense equivalent to Atanassov fuzzy sets (AFS, see [1]), which however were originally devised as F1 and B2 objects. In fact, as a consequence of this formal equivalence, a bitter dispute (see [10] and [3]) raised between Atanassov and his followers, on one side, and an important part of the fuzzy community, on the other, about the exact meaning of AFS and their real relevance in the context of bipolarity.…”