Rough set extensions in incomplete information systems

All eight possible extended rough set models in incomplete information systems are proposed.By analyzing existing extended models and technical meth-ods of rough set theory,the strategy of model extension is found to be suitable for processing incomplete information systems instead of filling possible values for missing attributes.After analyzing the definitions of existing extended models,a new general extended model is proposed.The new model is a generalization of indiscernibility relations,tolerance relations and non-symmetric similarity relations.Finally,suggestions for further study of rough set theory in incomplete informa-tion systems are put forward.