“…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. For example, the variation nb rooms ≤ : S × S → {0, 1} maps a pair of apartments to 1 if the number of rooms increases, and to 0 otherwise, and the co-variation (nb rooms ≤ = 1) → (price ≤ = 1) expresses that if the number of rooms of an apartment increases, then the price also increases.…”