Querying fuzzy relational databases through fuzzy domain calculus

In this paper we present a definition of a domain relational calculus for f uzzy relational databases using the GEFRED model as a starting point. It is possible to define an equivalent fuzzy tuple relational calculus and conse quently we achieve the two query language levels that Codd designed for rel ational databases but these are extended to fuzzy relational databases: Fuz zy relational algebra (defined in the GEFRED model) and the fuzzy relationa l calculus which is put forward in this paper. The expressive power of this fuzzy relational calculus is demonstrated through the use of a method to t ranslate any algebraic expression into an equivalent expression in fuzzy do main relational calculus. Furthermore, we include a useful system so that t he degree to which each value has satisfied the query condition can be meas ured. Some examples are also included in order to clarify the definition. ( C) 1999 John Wiley & Sons, Inc.