Leonid Tineo

SQLf3: an extension of SQLf with SQL3 features

Fuzzy Logic has been proposed for information representation and manipulation in databases, being the current tendency to study mechanisms of flexible querying to traditional databases. SQLf has been one of the efforts in this tendency. On the other hand, there are many different dialects of SQL. There are two major standards: ANSI (American National Standards Institute) SQL and an updated standard adopted in 1992, called SQL-92 or SQL2. There is also an emerging standard called SQL3 that extends SQL2 with many new features such as recursion, triggers, and objects. Then, there are versions of SQL produced by the principal vendors of database management systems. This paper looks for to continue the contribution in the area flexible querying to relational databases. Basically this contribution embraces the definition of the flexible querying language SQLf3 according to those characteristics contemplated in the norms SQL3 that can be susceptible to a fuzzy treatment.

SQLf flexible querying language extension by means of the norm SQL2

Traditional information storage and recovery systems are based on classic logic and set theory, limiting the user when he wants to express preferences. Fuzzy logic has been proposed for information representation and manipulation in databases, being the current tendency to study mechanisms of flexible querying to traditional databases. SQLf has been one of the efforts in this tendency. On the other hand, there are many different dialects of SQL. There are two major standards: ANSI (American National Standards Institute) SQL and an updated standard adopted in 1992, called SQL-92 or SQL2. This paper looks for to continue the contribution in the area flexible querying to relational databases. Basically this contribution embraces the definition of the flexible querying language SQLf2 according to those characteristics contemplated in the norms SQL2 that can be susceptible to a fuzzy treatment.

Fuzzy dominance skyline queries

Skyline is an important and recent proposal for expressing user preferences. While no one best row exists, Skyline discards rows which are worse on all criteria than some other and retrieves non-dominated or the best ones that match user preferences. Nevertheless, some dominated rows could be interesting to user requirement, but they will be rejected by Skyline. Dominated rows could be discriminated (or ranked) by means of user preferences, but Skyline only discards dominated ones and it does not discriminate them. SQLf is a proposal for preferences queries based on fuzzy logic that allows to discriminate rows and includes user-defined terms, such as fuzzy comparison operators. In this work, we propose to flexibilize Skyline queries using fuzzy comparison operators in order to retrieve interesting dominated rows. We also introduce an evaluation mechanism for these queries and our initial experimental study shows that this mechanism has a reasonable performance.

A New Upgrade to SQLf: Towards a Standard in Fuzzy Databases

One remarkable fuzzy set based extension to SQL is SQLf. It allows fuzzy conditions in any place where SQL allows a Boolean one. At present time SQLf development is not up to date with SQL standard. Latest SQLf revision was with the SQL:1999 standard.New features of SQL:2003 standard have not been yet extended to the fuzzy case in SQLf. In this paper, we make a contribution towards a standard in Fuzzy Databases, upgrading SQLf according SQL:2003standard, proposing these new fuzzy features: fuzzy table storage,fuzzy multiset data type and fuzzy merge statement.

Flexible query processor for information

A formalism is presented for the design of an information retrieval system, where the document and query representation, the function of matching among the documents stored, as well as the requests, and finally the retrieved results ranked by the retrieval status value are defined. Also, a small implementation is shown by a prototype.

About the Performance of SQLf Evaluation Mechanisms

In order to make more flexible database access the query language SQLf has been previously proposed. One of the SQLf features is the use of Fuzzy Quantifiers in Having Clause. For this kind of query, three evaluation mechanisms have been proposed: the Naive, the Sugeno Integral Heuristics based and the Alfa-cut Derivation based. We present in this paper a formal performance study of these three mechanisms. This s tudy has been made using a SQLf prototype build on top of a RDBMS.

On the Performance of Fuzzy Data Querying

We are interested in providing databases with fuzzy data representation and flexible querying capabilities. This work concerns with a performance analysis based on statistical techniques to evaluate methods for fuzzy queries over fuzzy data. We introduce the application of Derivation Principle for this kind of queries and show its practical benefit using a prototype that we have built on top of Oracles DBMS.

SQLf vs. Skyline - Expressivity and Performance

SQL has limitations in order to express user preferences. The ORDER BY clause is a way to express preferences, but it is complicated to manage criteria that involve three or more conditions. Skyline operator is a simple way of specifying user preferences extending SQL, but has high processing time when its algorithms are evaluated. SQLf is another SQL extension for user preference based on fuzzy logic whose algorithms can be less expensive. This work compares SQLf and Skyline approaches in terms of time and number of returned answers. Also, we compare the expressive power of both SQLf and Skyline languages.

Derivation Principle in Advanced Fuzzy Queries

Traditional information storage and recovery systems are based on classic logic and set theory, limiting expression of user preferences. Fuzzy logic has been proposed for information representation and manipulation in databases, being the current tendency to study mechanisms of flexible querying to crisp databases. SQLf has been one of the efforts in this tendency. The authors presented the use of the lambda-cut for processing fuzzy queries involving advanced constructor blocks in both SQLf2 and SQLf3. These languages are evolutions of SQLf according to both SQL2 and SQL3 norms with fuzzy set based extensions. The scope of this work is queries with predefined quantifiers, recursive queries, views, subqueries and case constructor. Preceding works have defined the use of lambda-cut for the evaluation of fuzzy queries as the derivation principle. This principle has been used before for other kind of queries in SQLf

The Egloo Fuzzy Web Data Source Selection Tool

The WWW is a very large repository composed of many documents that are stored by several data sources. Web search engines allow retrieval based on keywords. Nevertheless, published documents may be incomplete, obsolete or huge. Therefore, search also might include quality criteria such as completeness, recentness, update frequency, and granularity. Traditional DBMS rigidity does not allow the expression of user preferences based on soft criteria. Fuzzy DBMS, such as SQLfi, are necessary instead. Here we present a tool for the selection of the best data sources and documents in terms of user preferences. Documents and data sources would be described according to quality parameters stored in a catalog. Retrieval would be done by means of fuzzy SQLf queries. Our tool offers a user-oriented wizard to allow the expression of requirements.