Rough Sets Dealing with Possibilistic Information

Abstract

Rough sets are examined in information tables containing possibilistic information. It is known that rough approximations are not unique, but are obtained in the form of lower and upper bounds of the actual rough approximations. Only possible rough approximations, the upper bound of the actual rough approximations, are examined in the previous studies. This paper describes rough approximations by formulating certain rough approximations as well as possible ones.