Improvement to the Criterion ω(x, y) in Positive Reduct of Decision Table

The paper makes improvement to the condition omega(x,y) which the elements in discernibility matrix introduced by Skowron satisfy. Thus we can get two advantages: the verification to the condition is simpler; the elements satisfying the condition in discernibility matrix are less. Then the complexity of computing reduct with discernibility function decreases. Such property is effective not only to manual operation but also to computer processing. The paper is organized as follows: Firstly, the starting point of the idea in this paper is presented vividly from two facets in the positive region chart; Secondly, we give the proof to the improved condition; Lastly, we illustrate the validity of the improved condition.