Bustince, HumbertoBarrenechea, EdurneFernández, JavierPagola, MiguelMontero De Juan, Francisco JavierKacprzyk, JanuszPedrycz, Witold2023-06-192023-06-192015Bustince, H., Barrenechea, E., Fernández, J., Pagola, M., Montero, J.: The Origin of Fuzzy Extensions. En: Kacprzyk, J. y Pedrycz, W. (eds.) Springer Handbook of Computational Intelligence. pp. 89-112. Springer Berlin Heidelberg, Berlin, Heidelberg (2015)978-3-662-43504-510.1007/978-3-662-43505-2_6https://hdl.handle.net/20.500.14352/35748Many different kinds of sets have been defined within the framework of fuzzy sets . This paper focusses on those fuzzy set extensions that address the difficulties that experts find in order to build the membership values. In particular, we analyze type-2 fuzzy sets , interval-valued fuzzy sets , Atanassov’s intuitionistic fuzzy sets , or bipolar sets of type-2 and Atanassov’s interval-valued fuzzy sets. After stating a general approach to these extensions, we remark some structural problems in the extension problem and stress some applications for which the results obtained with extensengbook parthttps//doi.org/10.1007/978-3-662-43505-2_6http://link.springer.com/chapter/10.1007%2F978-3-662-43505-2_6restricted access510.64Lógica simbólica y matemática (Matemáticas)1102.14 Lógica Simbólica