Logical difference model of grade upper approximation operator and grade lower approximation operator

Grade is an important quantitative index, and graded rough set model is an important improved rough set model. This paper is to explore new improved rough set model. Based on logical difference operation of grade approximation operators, it proposes logical difference model of grade upper approximation operator and grade lower approximation operator. In the new model, basic structure and properties are obtained, and macroscopic algorithm and structural algorithm are proposed. Finally logical difference model of grade upper approximation operator and grade lower approximation operator is explained by a medical example.