Handling fuzzy information in extended possibility-based fuzzy relational databases

Abstract

Two kinds of fuzziness in attribute values of the fuzzy relational databases can be distinguished: One is that attribute values are possibility distributions, and the other is that there are resemblance relations in attribute domains. The fuzzy relational databases containing these two kinds of fuzziness simultaneously are called extended possibility-based fuzzy relational databases. In this paper, we focus on such fuzzy relational databases. We classify two kinds of fuzzy data redundancies and define their removal. On this basis, we define fuzzy relational operations in relational algebra, which, being similar to the conventional relational databases, are complete and sound. In particular, we investigate fuzzy querying strategies and give the form of fuzzy querying with SQL.

Updating extended possibility-based fuzzy relational databases

“…18, five primitive operations in the fuzzy relational databases, including union, difference, Cartesian product, selection, and projection, and three additional operations intersection, join, and division, as well as rename and outerunion operations are defined. In the following, we only focus on union, difference, and selection operations.…”

“…The full definitions of relational operations in the fuzzy relational databases can be found in Ref. 18.…”

“…8,[12][13][14][15] Also there have been research studies on fuzzy query languages 16,17 and fuzzy relational algebra. 9,18 In Ref. 16, an existing query language, namely, SQL, for fuzzy queries was extended and some fuzzy aggregation operators were developed.…”

A New Functional Dependency in a Vague Relational Database Model

“…Fuzzy set theory, introduced by Zadeh in 1965 [1] has been widely used in literature [2,3,4,5,6,7,8,9] to incorporate such imprecise data into classical relational databases. Extensive research has been carried out in this direction and several fuzzy relational database models have been proposed to model vague information in relational databases.…”

“…Extensive research has been carried out in this direction and several fuzzy relational database models have been proposed to model vague information in relational databases. Also, based on such fuzzy relational models, there have been many studies on different data integrity constraints [2,3,4,8,9], fuzzy relational algebra [5], fuzzy query languages [10] and so on. However, vague set theory was put forward by Gau and Buehrer [11] in 1993 as a more efficient tool to deal with imperfect or ambiguous data.…”