关键词: 粗糙集, 不完备信息系统, 容差关系, 非对称相似关系, 限制容差关系, 改进的二元关系

Abstract: In order to process incomplete information systems，the classical rough set theory needs to be extended.In this paper，the incomplete information system is investigated.In such information systems，a new relation is proposed which is based on one parameter，and the rough set model is based on this new relation.An extended model is obtained，which is more effective in classification if setting the parameter properly.It is proved that the new model can anticipate and classify data more precisely.A practical example has verified the advantage of the new binary relation and the extended model.

Key words: rough set, Incomplete Information System（IIS）, tolerance relation, non-symmetrical similarity relation, limited tolerance relation, improved binary relation