On topological properties of generalized rough sets

In this note we consider topological properties of generalized rough sets. In any approximation space (X,R) of a generalized rough set we show that 1. If R is reflexive, then the set OR={A⊆X|R-(A)=A} defined by R-is a topology on X; 2. If R is reflexive and symmetric, then the topology OR has the following property (Clop) A : open A : closed 3. Conversely, for any topology O with (Clop), there is a reflexive and symmetric relation R on X such that O=OR.