“…Even a very specific rule, when learned with a support of 1 as in the previous paragraph, may be dubious, because it amounts to single instance induction. Several works [11,17,28,91] have emphasized the idea that the rules ( σ S = α) → ( σ R = β) that are reasoned upon should be functional dependencies, i.e., have a confidence value of 1 on any two pairs of cases of the case base. From this observation, [5] defined a variation as any function that associates a value to a pair of situations, and a co-variation as a functional dependency between variations.…”