ABSTRACT
In this chapter, we present the fundamentals of classical set theory, fuzzy sets, and rough sets that can be used to express opinions. Basic operations for these sets are defined and demonstrated. Fuzzy relations and fuzzy arithmetic can be used to express and combine collected information. The fundamentals of probability theory, possibility theory, interval probabilities, and monotone measures will be summarized as they relate to the expression of expert opinions. Examples are used in this chapter to demonstrate the various methods and concepts.
