Vagueness, under its many names and forms (unsharp predicates, uncertainty, approximate and/or incomplete/inexact reasoning, partial knowledge and incomplete information, approximation, and so on), pervades many scientific theories. As soon as vagueness is introduced in a theory, the need for control and for the design of efficient, quantitative methods to exert such control arises. Oddly, such urge is even more present in the very disciplines that could more easily displace it, namely Computer and Information Sciences.