SQLf flexible querying language extension by means of the norm SQL2

Traditional information storage and recovery systems are based on classic logic and set theory, limiting the user when he wants to express preferences. Fuzzy logic has been proposed for information representation and manipulation in databases, being the current tendency to study mechanisms of flexible querying to traditional databases. SQLf has been one of the efforts in this tendency. On the other hand, there are many different dialects of SQL. There are two major standards: ANSI (American National Standards Institute) SQL and an updated standard adopted in 1992, called SQL-92 or SQL2. This paper looks for to continue the contribution in the area flexible querying to relational databases. Basically this contribution embraces the definition of the flexible querying language SQLf2 according to those characteristics contemplated in the norms SQL2 that can be susceptible to a fuzzy treatment.