Rough Approximation of Fuzzy Concepts in Weak Approximation Spaces

The purpose of this paper is to present a new approach determining the rough approximations of fuzzy concepts in fuzzy decision systems. Based on the hierarchical characteristic of fuzzy sets, a lambda- weak fuzzy approximation space and a CN_lambda -fuzzy rough set, determined by an inclusion function and a near function, are introduced. Some properties of the near function and CN_lambda-fuzzy rough sets are investigated. Therefore, the lower and upper approximations of a fuzzy decision concept can be derived from the description of inclusion nearness with respect to the fuzzy decision concept.