Rough set theory and three way decisions: Refinement of boundary region in the decision making process

Rough Set Theory is widely used for successful decision making. Problems of real life situation demands multiple way decisions and conventional two way decision system have to be refined to make effective decisions. From the lower and upper approximations of Pawlak Rough Set model, three disjoint regions in the universe have been derived and a three way view model for decision making is proposed in this paper. The basic principles of Rough Set Theory are explained along with suitable examples. Decision making becomes more difficult when data sets are vague and uncertain. A method to refine the boundary region is also presented in this paper to make more deterministic decisions. The proposed method was able to reduce the size of the boundary region considerably and more deterministic decisions could be arrived using this method. However, there exists a cost in the accuracy of the decisions made using this method.