On a fuzzy bipolar relational algebra

Some issues of fuzzy querying in relational databases

“…The third approach for bipolar queries is based on the lexicographic ordering [10]. In this approach degrees for N and P are evaluated separately, i. e. no aggregation between the constraint and the wish is performed.…”

“…A tuple which is beaten on the constraint cannot win even if it is notably better on the wish [10]. A tuple which is equal on the constraint wins, if it is even slightly better on the wish.…”

Fuzziness in database management systems: Half a century of developments and future prospects

“…For more information on various aspects of bipolar queries which attract more and more attention, we refer to, for instance: [85,8,29,31,63,60,61,64,66], etc.…”

On a Graded Inclusion of Bipolar Fuzzy Relations

“…In previous works, we have defined a fuzzy bipolar relational algebra [7], as well as a bipolar version of the fuzzy query language SQLf [20]. In this paper, our aim is to extend this latter work by considering new types of queries, namely those involving inclusion-based conditions.…”

“…Several definitions have been proposed, cf. [6,18,7]. Let us consider for instance the definition from [18], which is recalled hereafter.…”