Abstract: Set-valued information systems, in which some objects may have more than one value for an attribute, are generalized complete information systems. Introducing a neighborhood relation to set valued information systems,we established a rough set approach based on the neighborhood of every object as elementary set. Furthermore, in order to simplify knowledge representation, we proposed the concept of neighborhood consistent set and neighborhood reduction,and discussed the properties and judgments of neighborhood consistent set. Finally, we obtained the approach to compute neighborhood reduction for set valued information systems by the discernibility function.

Key words: Set valued information system, Neighborhood, Neighborhood reduction, Discernibility function