Rough set methods based on discernibility relationship in IIS

Classical rough set theory based on indiscernibility relationship rarely concerns discernibility relationships. However discernibility relationship deserves more attention because of its higher efficiency. In this paper a new kind of discernibility relationship is defined for studying incomplete information system. To demonstrate the validity of discernibility relationship, first we give a precise definition of discernibility relationship before the corresponding lower and upper approximations can be computed. Next the major properties of the lower and upper approximations can be obtained and proved. Finally the rough set model based on discernibility relationship is so easily constructed.