A Fuzzification of the Relational Data Model

Expression and processing of vagueness, which has many real world applications, is not handled effectively in the conventional relational model. In this paper we investigate a fuzzy extension to the relational data model and propose three fuzzy relational query languages. ‘ho of them are the Level-l Fuzzy Relational Algebra and Level-l Fmzy Relational Calculus. They are fundamental query languages and serve as a theoretical framework for the fuzzy relational database. Based on them, the Fuzzy Selective Relational AIgebrn is presented to express fuzzy constants and fuzzy comparators, which are more effective to represent vagueness in user queries. We show that the three proposed query languages have the same expressive powers.