2. Fuzzy logic

Let's start with a convenient representation. What was introduced in (7) and (8) is called, in classical set theory, a characteristic function. Now, let's suppose that v (x ), instead of taking the value 0 or 1, can take any value in the interval [0,1]. Thus, an element x could belong to the frame of reference with a value between 0 and 1 too. A subset whose elements have this property is called a fuzzy subset.

Thus :

A fuzzy subset will then be denoted