Real world is featured with complex phenomenons. As uncertainty is inevitably involved in problems arise in various Öelds of life and classical methods failed to handle these type of problems. Dealing with imprecise, uncertain or imperfect information was a big task for many years. Many models were presented in order to properly incorporate uncertainty into system description, LotÖ A.Zadeh in 1965 introduced the idea of a fuzzy set. Zadeh replaced conventional characteristic function of classical crisp sets which takes on its values in f0; 1g by membership function which takes on its values in closed interval [0; 1]. Fuzzy set theory is conceptually a very powerful technique to deal with another aspect or vision of imperfect information related to vagueness and is a modelling tool for complex systems that can be controlled by human but very tough to deÖne exactly