Rough set model in incomplete and fuzzy decision information system based on improved-tolerance relation

The topical rough set theory is a forceful tool to handle the complete information system, and its effect to process incomplete information system is poor, particularly, its function to combine the incomplete information system with fuzzy decision information system is poorer. On the base of improving on the tolerance relation made by M. Kryszkiewez, this paper proposes the improved-tolerance relation and improved-tolerance classes; we simultaneously present the definition of the incomplete and fuzzy decision information system based on the improved-tolerance relation, and give its rough set model, i.e. the rough set model in incomplete and fuzzy decision information system. Finally, the conception of precision reduction is defined, and its algorithm is also supplied.