Derivation Principle in Advanced Fuzzy Queries

Traditional information storage and recovery systems are based on classic logic and set theory, limiting expression of user preferences. Fuzzy logic has been proposed for information representation and manipulation in databases, being the current tendency to study mechanisms of flexible querying to crisp databases. SQLf has been one of the efforts in this tendency. The authors presented the use of the lambda-cut for processing fuzzy queries involving advanced constructor blocks in both SQLf2 and SQLf3. These languages are evolutions of SQLf according to both SQL2 and SQL3 norms with fuzzy set based extensions. The scope of this work is queries with predefined quantifiers, recursive queries, views, subqueries and case constructor. Preceding works have defined the use of lambda-cut for the evaluation of fuzzy queries as the derivation principle. This principle has been used before for other kind of queries in SQLf