Abstract
The fuzzy sets allow for the representation of vague concepts, where membership of an object could be gradual. The use of this theory in the data bases has been proposed. As result of that, the fuzzy relational model GEFRED has emerged, as well as the fuzzy extended Entity-Relationship model FuzzyEER and the fuzzy querying language FSQL, among others. These extensions include some forms of fuzzy attributes, such as the so-called Type 3. These attributes have values in a set of labels provided with a fuzzy similarity relation, which is an extension of equivalence relations in the fuzzy set theory. The implications of such attributes in partitioned query operators have not been previously explored. The contribution of this paper is on the syntactic and semantic definition of an extension to SQL, in order to allow for partitioned queries with Type 3 fuzzy attributes in grouping criteria. This extension increases the expressive power of the database language with respect to previous proposals
Highlights
The fuzzy sets allow for the representation of vague concepts, where membership of an object could be gradual
The fuzzy relational model GEFRED has emerged, as well as the fuzzy extended Entity-Relationship model FuzzyEER and the fuzzy querying language FSQL, among others. These extensions include some forms of fuzzy attributes, such as the so-called Type 3
These attributes have values in a set of labels provided with a fuzzy similarity relation, which is an extension of equivalence relations in the fuzzy set theory
Summary
Recibido 19 de agosto de 2013, aceptado 8 de mayo de 2014 Received: August 19, 2013 Accepted: May 8, 2014. Se ha propuesto el uso de esta teoría en bases de datos. Como resultado ha surgido el modelo relacional difuso GEFRED, el modelo entidad relación extendido difuso FuzzyEER y lenguaje de consultas difusas FSQL, entre otros. Estas extensiones incluyen algunas formas de atributos difusos, como los llamados Tipo 3. Estos atributos toman valores de un conjunto de etiquetas provisto de una relación difusa de similitud, que es una extensión de las relaciones de equivalencia en la teoría de conjuntos difusos. La contribución del presente artículo consiste en la definición sintáctica y semántica de una extensión a SQL para permitir consultas particionadas difusas basadas en atributos Tipo 3. Esta extensión aumenta la expresividad del lenguaje de bases de datos, respecto de propuestas anteriores. Palabras clave: SQL, consultas difusas, relaciones de similitud, atributos difusos, GROUP BY
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