Florentin Smarandache's representation of the probability of an event occuring, given by T, I, F which are real subsets representing the truth, indeterminacy, and falsity percentages respectively, and
n_sup = sup(T) + sup(I) + sup(F) < 100
Related to intuitionistic logic.
[Florentin Smarandache, "A Unifying Field in Logics. / Neutrosophy: Neutrosophic Probability, Set, and Logic", American Research Press, Rehoboth 1999].