Granular structures of fuzzy rough sets based on general fuzzy relations

Existing studies on the granular structures of fuzzy rough sets are mainly proposed based on the T-similarity relations which are only a special kind of fuzzy relations. Therefore, it is of interest to extend the study to more general situations in order to expand the application scope of the fuzzy rough set theory. In this paper, the granular structures of the S-lower, T-upper, #-lower and crupper approximations of the fuzzy sets are established based on more general fuzzy relations.