A reactualization formula for joining multiple classes in hierarchical classification

The paper considers the frequently observed situation where several class pairs correspond-simultaneously-to the highest value of the proximity index between classes, in the building of hierarchical classification, by an agglomerative procedure. The usual way consists of applying several times a reactualization formula, before going on the next level of the classification tree. It proposes only one reactualization, by the means of a formula taking into account the joining of more than two classes. This formula is established for the most classical association criteria between classes.