Abstract
In this paper, we study rough sets in incomplete information tables, which are data sets containing some missing values. We proposed a rough set approach to incomplete information tables. In the proposed approach, object sets are represented by pessimistic and optimistic approximations. These approximations deal with uncertainty caused by not only indiscernibility of objects but also missing values. Moreover, we introduce the concept of the variable precision rough set approach into the proposed approach. As a result, the membership degrees of objects to a set of object become intervals.
