关键词: 集合, 关系积, 属性, 粗糙集, 值约简

Abstract: The value reduction is an important research topic in Rough Set（RS） theory.Because value reduction is a NP-hard problem，there is no effective algorithm to get the minimal value reduction at present.The attribute reduced procedure is translated to find the attribute union based on the set theory，reducing the number of scanning the decision table and improving the reduced efficiency；Using the information derived from the attribute reduction algorithm，the minima value reduction table is obtained and this NP-hard problem is solved.

Key words: set theory, attribute union, attribute, rough set, value reduction