The Simplify Algorithm of Calculating the Reduced Differential Matrix Is Untenable
计算约简的差别矩阵简化算法不成立

Skowron's differential matrix theory makes the reduce processes of rough set more simple. But the shortness of this method is that it requires that the intermediate links of the differential matrix is produced and stored, which creates wastes on time and space. A simplified method is given in practice: on the one side, it extracts the differential elements to construct conjunctive normal form from the information table. On the other side, it uses distribution law and absorption law as the equivalence transformation of the logical formula to get the minimum disjunctive normal forms directly. This paper gives the anti-examples to show that the simplify algorithm is untenable.