Knowledge reductions in fuzzy information systems

Knowledge reduction is one of important issues in rough sets theory. Based on rough set models and knowledge reduction definitions, researching on the corresponding reduction methods is primary approach in knowledge reductions. In symbolic information systems, knowledge reduction definitions and algorithms are in depth examined, in which researches are concentrated on discernibility matrix and functions, heuristic algorithms, incremental algorithms, etc. Information systems are named as fuzzy information systems in which all values are fuzzy. In fuzzy information systems, some basic rough set models are presented, which are called fuzzy-rough set methods. In this paper, definitions of knowledge reductions in fuzzy information systems are improved, that is, some new knowledge reductions are proposed.