Fuzzy querying with SQL: extensions and implementation aspects

Abstract All the DBMS commercially available provide querying capabilities that are based on Boolean selection. Consequently, it is possible to express conditions applying to individual tuples or sets of tuples. However, this characteristic turns out to be a severe limitation when some types of applications are under consideration. Especially, we have been led to deal with an application, called HAVANE, that gave rise to two main constraints: the number of answers has to be controlled and some parts of queries are not Boolean conditions. So, we turn towards an extension of DBMS querying capabilities in order to allow fuzzy queries against a usual database, i.e. composed of precise facts. Thus an extension of the well-known language SQL is presented along with some considerations about how such fuzzy queries can be processed to get acceptable performances.