This paper presents a representation language based on Rough Set theory,called RSL．This language has tWO parts：one is for application and the other for theory research．The application part is designed mainly for information analysis，such as data analyses and decision making．The research part tries to provide a tool for researchers on theory or on constructing more complicate algorithms．Finding the smallest reduction has been proved tO be an NP-complete problem，a domain-independent approximate algorithm is presented in this paper．It makes the RSL more suitable tO deal with large information tables．