Computable Database Queries and the Expressiveness of the Relational Algebra

1999 ◽  
pp. 359-384
Author(s):  
Mark Levene ◽  
George Loizou
Keyword(s):  
Relational Algebra ◽  
Database Queries

FROM SEMANTICOBJECTS TO STRUCTURED NATURAL LANGUAGE

2007 ◽  
Vol 01 (03) ◽  
pp. 359-375 ◽  
Author(s):  
PHILLIP C-Y. SHEU ◽  
ATSUSHI KITAZAWA ◽  
CHIHIRO ISHII ◽  
KENICHI KANEKO ◽  
FEI XIE
Keyword(s):  
Natural Language ◽  
Relational Algebra ◽  
Database Queries ◽  
Object Relational ◽  
Meta Information

This paper presents a structured natural language (SNL) based on an object-relational algebra that allows users pose database queries whose scope is much wider than that of the relational algebra. We also discuss how queries expressed in natural language (NL) may be translated into SNL using meta-information.

scholarly journals Computer Aided Verification of Relational Models by Strategic Rewriting

2017 ◽  
Vol 17 (02) ◽  
pp. e19
Author(s):  
Claudia Mónica Necco ◽  
José N. Oliveira ◽  
Joost Visser ◽  
Roberto Uzal
Keyword(s):  
Term Rewriting ◽  
Semantic Content ◽  
Relational Algebra ◽  
State Transitions ◽  
Software Modeling ◽  
Relational Models ◽  
Database Queries ◽  
Term Rewriting System ◽  
Static Checking ◽  
Functional Components

Binary relational algebra provides semantic foundations for major areas of computing, such as database design, state-based modeling and functional programming. Remarkably, static checking support in these areas fails to exploit the full semantic content of relations. In particular, properties such as the simplicity or injectivity of relations are not statically enforced in operations such as database queries, state transitions, or composition of functional components. When data models, their constraints and operations are represented by point-free binary relational expressions, proof obligations can be expressed as inclusions between relational expressions. We developed a typedirected, strategic term rewriting system that can be used to simplify relational proof obligations and ultimately reduce them to tautologies. Such reductions can be used to provide extended static checking for design contraints commonly found in software modeling and development.

Extending the Relational Algebra for Relations with Maybe Tuples and Existential and Universal Null Values

1984 ◽  
Vol 7 (1) ◽  
pp. 129-150
Author(s):  
Joachim Biskup
Keyword(s):  
Relational Algebra ◽  
Null Value ◽  
Null Values ◽  
A Minor

We study operations on generalized database relations which possibly contain maybe tuples and two types of null values. The existential null value has the meaning “value at present unknown” whereas the universal null value has the meaning “value arbitrary”. For extending a usual relational operation to generalized relations we develop three requirements: adequacy, restrictedness, and feasibility. As demonstrated for the natural join as an example, we can essetially meet these requirements although we are faced with a minor tradeoff between restrictedness and feasibility.

scholarly journals Multi-objective database queries in combined knapsack and set covering problem domains

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Sean A. Mochocki ◽  
Gary B. Lamont ◽  
Robert C. Leishman ◽  
Kyle J. Kauffman
Keyword(s):  
Relational Database ◽  
Set Covering ◽  
Covering Problem ◽  
Set Covering Problem ◽  
Database Queries ◽  
Multi Objective ◽  
Data Representations ◽  
Np Hard Problem ◽  
Institute Of Technology ◽  
The One

AbstractDatabase queries are one of the most important functions of a relational database. Users are interested in viewing a variety of data representations, and this may vary based on database purpose and the nature of the stored data. The Air Force Institute of Technology has approximately 100 data logs which will be converted to the standardized Scorpion Data Model format. A relational database is designed to house this data and its associated sensor and non-sensor metadata. Deterministic polynomial-time queries were used to test the performance of this schema against two other schemas, with databases of 100 and 1000 logs of repeated data and randomized metadata. Of these approaches, the one that had the best performance was chosen as AFIT’s database solution, and now more complex and useful queries need to be developed to enable filter research. To this end, consider the combined Multi-Objective Knapsack/Set Covering Database Query. Algorithms which address The Set Covering Problem or Knapsack Problem could be used individually to achieve useful results, but together they could offer additional power to a potential user. This paper explores the NP-Hard problem domain of the Multi-Objective KP/SCP, proposes Genetic and Hill Climber algorithms, implements these algorithms using Java, populates their data structures using SQL queries from two test databases, and finally compares how these algorithms perform.

Incomplete information in a relational database

1980 ◽  
Vol 3 (3) ◽  
pp. 363-377
Author(s):  
John Grant
Keyword(s):  
Incomplete Information ◽  
Relational Database ◽  
Functional Dependency ◽  
Relational Algebra ◽  
Database Model ◽  
Character String

In this paper we investigate the inclusion of incomplete information in the relational database model. This is done by allowing nonatomic entries, i.e. sets, as elements in the database. A nonatomic entry is interpreted as a set of possible elements, one of which is the correct one. We deal primarily with numerical entries where an allowed set is an interval, and character string entries. We discuss the various operations of the relational algebra as well as the notion of functional dependency for the database model.

SQL query optimization through nested relational algebra

2007 ◽  
Vol 32 (3) ◽  
pp. 18 ◽  
Author(s):  
Bin Cao ◽  
Antonio Badia
Keyword(s):  
Query Optimization ◽  
Relational Algebra ◽  
Sql Query
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