Unique negative dimension
Unique negative dimension (UND) is a complexity measure for the model of learning from positive examples. The unique negative dimension of a class formula_1 of concepts is the size of the maximum subclass formula_2 such that for every concept formula_3, we have formula_4 is nonempty. This concept was originally proposed by M. Gereb-Graus in "Complexity of learning from one-side examples", Technical Report TR-20-89, Harvard University Division of Engineering and Applied Science, 1989.