Prade, Henri; Testemale, Claudette Generalizing database relational algebra for the treatment of incomplete or uncertain information and vague queries. (English) Zbl 0552.68082 Inf. Sci. 34, 115-143 (1984). This paper deals with relational databases which are extended in the sense that fuzzily known values are allowed for attributes. Precise as well as partial (imprecise, uncertain) knowledge concerning the value of the attributes are represented by means of [0,1]-valued possibility distributions in Zadeh’s sense. Thus, we have to manipulate ordinary relations on Cartesian products of sets of fuzzy subsets rather than fuzzy relations. Besides, vague queries whose contents are also represented by possibility distributions can be taken into account. The basic operations of relational algebra, union, intersection, Cartesian product, projection, and selection are extended in order to deal with partial information and vague queries. Approximate equalities and inequalities modeled by fuzzy relations can also be taken into account in the selection operation. Then, the main features of a query language based on the extended relational algebra are presented. An illustrative example is provided. This approach, which enables a very general treatment of relational databases with fuzzy attribute values, makes an extensive use of dual possibility and necessity measures. Cited in 68 Documents MSC: 68P20 Information storage and retrieval of data Keywords:relational databases; possibility distributions; fuzzy subsets; relational algebra; partial information; vague queries; fuzzy relations; fuzzy attribute values PDFBibTeX XMLCite \textit{H. Prade} and \textit{C. Testemale}, Inf. Sci. 34, 115--143 (1984; Zbl 0552.68082) Full Text: DOI References: [1] Baldwin, J. F., A fuzzy relational inference language for expert systems, (Proceedings of the 13th IEEE International Symposium on Multiple-Valued Logic. 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