Definition 3. Overlapping rule: Given two rules R1: X1 → Y1 and R2: X2 → Y2, then R3: X1 ∨ X2 → Y1(conf (R1), sup(R1)) ∨ Y2(conf (R2), sup(R2)) is an overlapping rule if and only if X1 = X2 and Y1 ≠ Y2