“…It is a new mathematical tool to handle inexact, uncertain or vague knowledge and has been successfully applied to many fields such as machine learning, pattern recognition and data mining [6,7,13,17,20]. In order to meet various practical applications, rough set theory has been connected with other theories, such as fuzzy set theory [18,22], boolean algebra [21,23], topology [15,26,30], lattice theory [2,3,4,5,9,10] and so on.…”