Class-based reducts in DRSA

In an ordered decision information system, dominance-based rough set approach (DRSA) were used to compute reducts of the system which preserve the lower and upper approximations of upward union and downward union of decision classes. Recently, class-based reducts (L-reduct and U-reduct) which preserve respectively lower and upper approximates of each decision classes was proposed. In this paper, we modify the definition of U-reduct and propose the concept of U*-reduct which is comprehensive and convenient for drawing decision rules. We give an equivalent description of L-reduct and U*-reduct, and compute the L-reduct and U*-reduct utilizing discernibility function defined by discernibility sets of objects.