Bipolar SQLf: A Flexible Querying Language for Relational Databases
نویسندگان
چکیده
Flexible querying of information systems allows expressing complex preferences in user queries. Such preferences can be modeled by fuzzy bipolar conditions which are made of constraints c and wishes w and interpreted as ”to satisfy c and if possible to satisfy w”.We define in this article the main elements of the Bipolar SQLf language, which is an SQL-like querying language based on a bipolar relational algebra [11, 3]. This language is an extension of the SQLf language [2, 1]. Basic statements (projection, selection, etc.) are firstly defined in terms of syntax, evaluation and calibration. Then, complex statements, such as bipolar queries based on nesting operators are studied in terms of expression, evaluation, query equivalence and backward compatibility with the SQLf language.
منابع مشابه
Flexible SQLf query based on fuzzy linguistic summaries
Data is often partially known, vague or ambiguous in many real world applications. To deal with such imprecise information, fuzziness is introduced in the classical model. SQLf is one of the practical language to deal with flexible fuzzy querying in Fuzzy DataBases (FDB). However, with a huge amount of fuzzy data, the necessity to work with synthetic views became a challenge for many DB communi...
متن کاملExtending RDBMS for Allowing Fuzzy Quantified Queries
This paper is mainly concerned with the extension of database management systems querying capabilities, so that users may address queries involving preferences and get discriminated answers. The use of flexible predicates and linguistic quantifiers interpreted in the framework of the fuzzy set theory is advocated for defining a query language, called SQLf. This language extends the functionalit...
متن کاملHierarchical Fuzzy Sets to Query Possibilistic Databases
Within the framework of flexible querying of possibilistic databases, based on the fuzzy set theory, this chapter focuses on the case where the vocabulary used both in the querying language and in the data is hierarchically organized, which occurs in systems that use ontologies. We give an overview of previous works concerning two issues: firstly, flexible querying of imprecise data in the rela...
متن کاملCustomizable Flexible Querying in Classical Relational Databases
The need to flexibly query relational databases has been widely recognized as a means to improve the effectiveness of the retrieval in current systems using SQL for expressing information needs. The main inadequacy of the SQL language is caused by the crisp algebra on which it is founded that does not support the ranking of the results with respect to their relevance to user needs. In this book...
متن کاملIntegrating Data from Possibly Inconsistent Databases
We address the problem of data inconsistencies while integrating data sets from multiple autonomous relational databases. We start by arguing that the semantics of integrating possibly inconsistent data is naturally captured by the maximal consistent subsets of the set of all information contained in the collected data. Based on this idea, we propose a simple and intuitive semantical framework,...
متن کامل