Expert appraisements and counter-appraisements with experton processes

A tool for appraisements by a group of experts, the experton, is explained. A semantic valuation on 11 positions (endecadery logic) is used. This tool is peculiarly adapted to expert systems. The experton concept arises from theories of fuzzy sets, intervals of confidence and random sets. It is a very convenient tool to aggregate experts' opinions in such a way that a decrease of entropy is realized at the end of the process and not at the beginning. The T-norms and T-conorms are not linear. An experton is an extension of the concept of random set (probabilistic set) where an interval of probabilities is obtained for each level alpha in