关键词: 粗糙集, 不完备决策表, 正区域, 差别矩阵, 核

Abstract: Computing core of incomplete decision table is one of the most important researches in rough set theory.At present，the core algorithms of incomplete decision table are few.In many general algorithms of computing core，their time complexity is[O(|C|3|U|2)].To cut down the time complexity of the algorithms for computing core，the definition of discernibility matrix and the corresponding definition of the core are proposed.At the same time，it proves that the core is equivalent to the core based on the incomplete decision table.On this condition，a quick algorithm for computing core is designed with the discernibility matrix，whose time complexity is[O(|C||Upos||U|)].An emulate example is used to illustrate the efficiency of the new algorithm.

Key words: rough set, incomplete decision table, positive region, discernibility matrix, core