A New Method for Approximation of Class Unions Based on Dominance-matrix Within DRSA

Dominance-based rough set approach(DRSA) is an extension of classical rough set theory(RST).Approximation of class unions is a very important approach in DRSA.Aiming at the disadvantage of the classical method,this paper presents a new methodology for approximation of class unions based on dominance-matrix.It only needs to calculate the dominance-matrix and does not need to consider the preference relations one by one.Thus it greatly simplifies the process and decreases the computing complex by k times(where k is the number of the decision classes).Besides it is intuitive and efficient.The example illustrates its feasibility and efficiency.