This paper critically analyzes reduct construction methods at two levels. At a high level,one can abstract common alities from the

existing algorithms,and classify them into three basic groups based on the underlying control structures.At alow level,by adopting di® erent

heuristics or¯ tness functions for attributes election,one is able to derive most of the existing algorithms-This paper critically analyzes reduct construction methods at two levels. At a high level,one can abstract common alities from the

existing algorithms,and classify them into three basic groups based on the underlying control structures.At alow level,by adopting di® erent

heuristics or¯ tness functions for attributes election,one is able to derive most of the existing algorithms...