In this paper, we present an implementation strategy for a fuzzy querying system embedded in a regular DBMS. This system relies on the language SQLf that makes it possible to express a great variety of fuzzy queries. Experiments show that this implementation strategy induces performance gains with respect to existing strategies based on a loose (or milder) coupling between a fuzzy querying layer and a DBMS, that necessitate an external postprocessing so as to compute the result in the form of a fuzzy relation. We also describe a user-friendly interface aimed at helping nonexpert users express their fuzzy queries in an intuitive manner.

In this demonstration we present a complete fuzzy-set-based approach to preference queries that tackles the two main questions raised by the introduction of flexibility and personalization when querying relational databases: i) how to efficiently execute preference queries? and, ii) how to help users define preferences and queries? As an answer to the first question, we propose PostgreSQL_f, a module implemented on top of PostgreSQL to handle fuzzy queries. To answer the second question, we propose ReqFlex an intuitive user interface to the definition of preferences and the construction of fuzzy queries.