We first present the concept of duality appearing in order theory, i.e. the notions of dual isomorphism and of Galois connection. Then we describe two fundamental dualities, the duality extension/intention associated with a binary relation between two sets, and the duality between implicational...

The problem of getting an homo-geneous group of elements linked to various kinds of fuzzy relations is presented often in several decision areas. It is possible to solve it by applying the affinity concept that allows grouping items that meet certain characteristics in a degree. Poverty is a key...