Abstract
Goal of this work is to present in a schematic way several methods, classical and not, to formally represent data whose non-exactness has to be made explicit, trying to highlight the different expressive power of such methods and their reciprocal relationships. The non-exactness is modeled in terms of imprecision and uncertainty, and for the formalization of such characteristics in particular fuzzy sets and fuzzy measures are introduced respectively, with their meaning and basic properties. The work, although not presenting a technical original contribution, offers a synthetic and easily understandable introduction to the quoted formal methods and a comparative critical analysis to them.