Generalized rough set under formal context and its application in expert system

Rough set theory and the theory of concept lattices are two efficient tools for knowledge discovery. Since an information system, the data description of rough set theory, and a formal context, the data description of concept lattice theory, can be taken as the other one. In this paper, generalized rough set model under formal context is discussed. Firstly, generalized lower and upper approximations of rough set are defined under formal context by means of information matrix. Secondly, the algorithm for getting the lower and upper approximation set is presented and new concepts of lower-matching degree and upper-matching degree are advanced. These concepts give a clearly clue and matting to the studies on rough set under formal context. Thirdly, the application of expert systems, based on the theory of generalized rough set under formal context, is introduced through medical expert systems. Finally the disadvantages and future research directions of rough set under formal context are discussed.