The exact express of the intersection and union of the fuzzy sets defined by the rough membership function is given . two extension model of rst are introduced and their characters are discussed . we also discover the changes of the upper ( lower ) approximation after the attributes were added to or removed from the original attribution set 首先得到了由粗糙隶属函数所定义模糊集的交与并的确切表达，改进了以往文献的结果；其次，提出了两种粗糙集的扩展模型，并对这两种模型的性质进行了讨论；最后，得出了属性集增加或删除属性后集合的上下近似的变化关系。
