Study on characteristic consistent blocks based rough set approach to incomplete system

In this paper, the incomplete information system with both absent and missing unknown values is deeply studied. Through characteristic relation, the limitation of characteristic class is pointed out such that not any two elements in a characteristic class are mutually tolerant. The technique of maximal consistent blocks is introduced into characteristic class and then the concept of characteristic consistent block is proposed, the corresponding rough set is then constructed. Not only the basic properties about characteristic consistent blocks based rough set are discussed, but also the relationship between characteristic consistent blocks and characteristic relation based rough sets are analyzed. It is shown that by comparing with the characteristic relation, we can obtain greater lower approximation and smaller upper approximation if characteristic consistent block approach is employed.