Many-level fuzzy rough approximation spaces induced by many-level fuzzy preorders and the related ditopological structures

摘要

We present a many-level version for the Pawlak - Dubois&Prade theory of rough approximation of fuzzy sets. Basing on the many-level upper and lower fuzzy rough approximation operators, we define the measure of rough approximation that in a certain sense characterizes the quality of the obtained approximation. Further, the fuzzy rough approximation operators give rise to two alternative topological-type structures considered in the paper.