Vague Set Theory and Its Application in Fuzzy Information Processing

Vague set theory and its different expressions are presented, the geometrical meaning of the expressions is interpreted, and the relations between vague sets and fuzzy sets are discussed. The development of vague sets is systematically discussed. Applications of the theory in decision-making, approximate reasoning and medical diagnosis are analyzed. Finally, problems existing in vague set theory and application, and directions of their further development are also proposed.