Abstract
Knowledge Discovery from Data (KDD) is the process of extracting useful knowledge by analyzing raw data. Fuzzy Set Theory is widely applied in Expert and Control Systems to cope with uncertain and imprecise knowledge. In this paper, we discuss the use of Fuzzy Set Theory in the KDD process. We present a survey of methods for fuzzy-coding of data, for fuzzy-representation of knowledge and for extracting fuzzy-knowledge from fuzzy-data.