Multi-Level Knowledge Reduction in Fuzzy Objective Information Systems

Knowledge reduction is one of the most important tasks in rough set theory. Aiming at fuzzy objective information systems (FOIS), several knowledge reductions, distribution reduction, maximum distribution reduction, assignment reduction and ordered assignment reduction, are defined under the condition of multi-level. The judgment theorem and discernibility matrix with respect to consistent set are obtained by means of the definitions. One method to extract the defined knowledge reductions is presented. This may aid to knowledge acquisition from fuzzy objective information systems