A Graded Rough Set with Variable Precision over Two Inconsistent and Related Universes

Classical one universe rough set is used on a lot of application in reality. But recent researches show that two universes rough set is more useful in practical application. We proposed a kind of graded rough set with variable precision which is over two inconsistent and related universes. The model solved the problem that the upper approximation can't contain the lower approximation which happened in other model. In the model, users can choose precision according their own requirements. It made the calculation more flexible. We gave the algorithm to calculate the approximations under variable precision, and gave the simple and convenient calculate method which used matrix.