A fuzzy database-query language

doi:10.1016/0306-4379(90)90030-S

Information Systems

Volume 15, Issue 5, 1990, Pages 583-590

https://doi.org/10.1016/0306-4379(90)90030-S Get rights and content

Abstract

Selection conditions for conventional database-query languages are not natural enough to express criteria with fuzzy concepts. To choose some alternatives from a database requires the techniques of multicriteria decision making or conflict resolution. However, some traditional techniques in this area still have some drawbacks, such as inefficiency and independency of criteria. In this paper a fuzzy database-query language is presented and its position in the area of multicriteria decisions making in database applications is discussed and identified. The selection constraints of this query language can accept both crispy and fuzzy conditions.

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A value-based approach to conflict resolution involving multiple objectives and multiple decision-making units

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Citation Excerpt :
It is the first implementation of a fuzzy database system. After that result, other researchers have proposed similar fuzzy extensions to the relational model such as in [6–9]. Another serious attempt to implement a fuzzy database system is given in [10,11].
Many years of research related to fuzzy logic and fuzzy set theory extensions to relational databases have not lead to stable implementations, standardized languages or fuzzy relational database application development tools and methods. The main goal of this paper is the modelling and the implementation of a set of tools that allow usage of fuzzy logic enriched with priorities in relational database applications. In order to achieve that goal, at first, the relational data model is extended with the elements of fuzzy set theory. After that, a fuzzy extension of the SQL query language, called the PFSQL, is defined. An interpreter for that language is integrated inside an implementation of the fuzzy JDBC driver. An implementation of the CASE tool for modelling of fuzzy relational database schemas rounds up a set of tools for the implementation of Java fuzzy database applications. In this sense, this paper presents a step towards a methodology for the fuzzy relational database application development.
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Users of information systems would like to express flexible queries over the data possibly retrieving imperfect items when the perfect ones, which exactly match the selection conditions, are not available. Most commercial DBMSs are still based on the SQL for querying. Therefore, providing some flexibility to SQL can help users to improve their interaction with the systems without requiring them to learn a completely novel language. Based on the fuzzy set theory and the α-cut operation of fuzzy number, this paper presents the generic fuzzy queries against classical relational databases and develops the translation of the fuzzy queries. The generic fuzzy queries mean that the query condition consists of complex fuzzy terms as the operands and complex fuzzy relations as the operators in a fuzzy query. With different thresholds that the user chooses for the fuzzy query, the user’s fuzzy queries can be translated into precise queries for classical relational databases.
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Expression and processing of vagueness, which has many real world applications, are not handled effectively in the conventional relational data model. In this paper we investigate a fuzzy extension to the relational data model and propose three fuzzy relational query languages. Two of them are the Level-1 Fuzzy Relational Algebra and Level-1 Fuzzy Relational Calculus. They are fundamental query languages and serve as a theoretical framework for the fuzzy relational database. Finally, the Fuzzy Selective Relational Algebra is presented to express fuzzy constants and fuzzy comparators, which are more effective to represent vagueness in user queries. We show that the three proposed query languages have the same expressive powers. We also present various aspects of the proposed model and its functional advantages over the conventional relational data model.
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A fuzzy database-query language

Abstract

Eur. J. Op. Res.

Multicriteria Decision Making

Dynamic conflict resolution through a theory of a displaced fuzzy idea

A concept of a fuzzy idea for multicriteria conflict resolution

A value-based approach to conflict resolution involving multiple objectives and multiple decision-making units