A Unified Treatment of Null Values Using Constraints

Kasim Candan, John Grant, V. S. Subrahmanian

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

An important reality when studying relational databases is the fact that entries in relational tables may often be "missing" or only partially specified. The study of such missing information has led to a rich body of work on "null values." It was recognized early on that there are many different types of null values, each of which reflects different intuitions about why a particular piece of information is missing. Different relations (or even the same relation) could contain different types of null values; yet, very little work has been done on providing a unifying model that reasons with different types of nulls. In this paper, we use constraints to provide a unifying framework for the most common types of nulls. We show how viewing tuples containing null values of these types can be viewed as constraints and how this leads to an algebra for null values. In particular, this algebra contains a unique operator (called the compaction operator) used to remove redundancies from null-valued relations. We have studied various properties of this algebra. We have built a prototype implementation based on the null-valued operators described here, and have conducted various experiments using this testbed.

Original languageEnglish (US)
Pages (from-to)99-156
Number of pages58
JournalInformation Sciences
Volume98
Issue number1-4
StatePublished - May 1997
Externally publishedYes

Fingerprint

Algebra
Null
Testbeds
Redundancy
Mathematical operators
Compaction
Operator
Relational Database
Testbed
Experiments
Tables
Prototype
Experiment

ASJC Scopus subject areas

  • Artificial Intelligence
  • Computer Science Applications
  • Information Systems
  • Information Systems and Management
  • Statistics, Probability and Uncertainty
  • Electrical and Electronic Engineering
  • Statistics and Probability

Cite this

Candan, K., Grant, J., & Subrahmanian, V. S. (1997). A Unified Treatment of Null Values Using Constraints. Information Sciences, 98(1-4), 99-156.

A Unified Treatment of Null Values Using Constraints. / Candan, Kasim; Grant, John; Subrahmanian, V. S.

In: Information Sciences, Vol. 98, No. 1-4, 05.1997, p. 99-156.

Research output: Contribution to journalArticle

Candan, K, Grant, J & Subrahmanian, VS 1997, 'A Unified Treatment of Null Values Using Constraints', Information Sciences, vol. 98, no. 1-4, pp. 99-156.
Candan K, Grant J, Subrahmanian VS. A Unified Treatment of Null Values Using Constraints. Information Sciences. 1997 May;98(1-4):99-156.
Candan, Kasim ; Grant, John ; Subrahmanian, V. S. / A Unified Treatment of Null Values Using Constraints. In: Information Sciences. 1997 ; Vol. 98, No. 1-4. pp. 99-156.
@article{0f33317a72804842ae5568cefad1649d,
title = "A Unified Treatment of Null Values Using Constraints",
abstract = "An important reality when studying relational databases is the fact that entries in relational tables may often be {"}missing{"} or only partially specified. The study of such missing information has led to a rich body of work on {"}null values.{"} It was recognized early on that there are many different types of null values, each of which reflects different intuitions about why a particular piece of information is missing. Different relations (or even the same relation) could contain different types of null values; yet, very little work has been done on providing a unifying model that reasons with different types of nulls. In this paper, we use constraints to provide a unifying framework for the most common types of nulls. We show how viewing tuples containing null values of these types can be viewed as constraints and how this leads to an algebra for null values. In particular, this algebra contains a unique operator (called the compaction operator) used to remove redundancies from null-valued relations. We have studied various properties of this algebra. We have built a prototype implementation based on the null-valued operators described here, and have conducted various experiments using this testbed.",
author = "Kasim Candan and John Grant and Subrahmanian, {V. S.}",
year = "1997",
month = "5",
language = "English (US)",
volume = "98",
pages = "99--156",
journal = "Information Sciences",
issn = "0020-0255",
publisher = "Elsevier Inc.",
number = "1-4",

}

TY - JOUR

T1 - A Unified Treatment of Null Values Using Constraints

AU - Candan, Kasim

AU - Grant, John

AU - Subrahmanian, V. S.

PY - 1997/5

Y1 - 1997/5

N2 - An important reality when studying relational databases is the fact that entries in relational tables may often be "missing" or only partially specified. The study of such missing information has led to a rich body of work on "null values." It was recognized early on that there are many different types of null values, each of which reflects different intuitions about why a particular piece of information is missing. Different relations (or even the same relation) could contain different types of null values; yet, very little work has been done on providing a unifying model that reasons with different types of nulls. In this paper, we use constraints to provide a unifying framework for the most common types of nulls. We show how viewing tuples containing null values of these types can be viewed as constraints and how this leads to an algebra for null values. In particular, this algebra contains a unique operator (called the compaction operator) used to remove redundancies from null-valued relations. We have studied various properties of this algebra. We have built a prototype implementation based on the null-valued operators described here, and have conducted various experiments using this testbed.

AB - An important reality when studying relational databases is the fact that entries in relational tables may often be "missing" or only partially specified. The study of such missing information has led to a rich body of work on "null values." It was recognized early on that there are many different types of null values, each of which reflects different intuitions about why a particular piece of information is missing. Different relations (or even the same relation) could contain different types of null values; yet, very little work has been done on providing a unifying model that reasons with different types of nulls. In this paper, we use constraints to provide a unifying framework for the most common types of nulls. We show how viewing tuples containing null values of these types can be viewed as constraints and how this leads to an algebra for null values. In particular, this algebra contains a unique operator (called the compaction operator) used to remove redundancies from null-valued relations. We have studied various properties of this algebra. We have built a prototype implementation based on the null-valued operators described here, and have conducted various experiments using this testbed.

UR - http://www.scopus.com/inward/record.url?scp=0031147895&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031147895&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0031147895

VL - 98

SP - 99

EP - 156

JO - Information Sciences

JF - Information Sciences

SN - 0020-0255

IS - 1-4

ER -