Dear Lotfi: I appreciate your idea about second-order multiplicity as a fruitful approach to random sets. But there is an additional application, once you introduce the proof of contradiction between a set in two different appearances. You mention the idea that " the elements are sets of elements drawn from a universe of discourse U". Exactly in this universe of discourse some variables may appear negated in certain statements, like transforming your example L={({a, b}, 2), ({c, d}, 3)} being a second-order multiset, into L={({-a, b}, 2), ({c, -d}, 3)}, which is also a second-order multiset.
Two decades ago I tried to follow this second approach in order to compare together laws, as approved by a legislative body, with the aim to discover contradictions among them. For a congressman working on a law proposal where there is primarily a need to satisfy a certain need of a given social or commercial or regional group. The large number of laws approved during one legislation period is a hindrance in the task to compare it with former laws in order to discover contradictions among them. Should we succeed in formulating laws not only in plain text, but also in logical formulas, the comparison would become more easy than before. Hence, I suggest to you to explore for example the laws of the state of California during the last legislative period and to find out if there is a reasonable approach to formulate them as logical formulas. Indeed, there is a large amount of experience from rule-oriented expert systems and Mamdani succeeded in applying them to fuzzy sets. I hope you can take some advantage from these ideas and find a new way to apply multisets to a practical purpose. Sincerely yours Salomon Klaczko D-12349 Berlin, Germany _______________________________________________ uai mailing list uai@ENGR.ORST.EDU https://secure.engr.oregonstate.edu/mailman/listinfo/uai