Publication
Title
Determining the currency of data
Author
Abstract
Data in real-life databases become obsolete rapidly. One often finds that multiple values of the same entity reside in a database. While all of these values were once correct, most of them may have become stale and inaccurate. Worse still, the values often do not carry reliable timestamps. With this comes the need for studying data currency, to identify the current value of an entity in a database and to answer queries with the current values, in the absence of reliable timestamps. This article investigates the currency of data. (1) We propose a model that specifies partial currency orders in terms of simple constraints. The model also allows us to express what values are copied from other data sources, bearing currency orders in those sources, in terms of copy functions defined on correlated attributes. (2) We study fundamental problems for data currency, to determine whether a specification is consistent, whether a value is more current than another, and whether a query answer is certain no matter how partial currency orders are completed. (3) Moreover, we identify several problems associated with copy functions, to decide whether a copy function imports sufficient current data to answer a query, whether a copy function can be extended to import necessary current data for a query while respecting the constraints, and whether it suffices to copy data of a bounded size. (4) We establish upper and lower bounds of these problems, all matching, for combined complexity and data complexity, and for a variety of query languages. We also identify special cases that warrant lower complexity.
Language
English
Source (journal)
ACM transactions on database systems. - New York, N.Y., 1976, currens
Publication
New York, N.Y. : 2012
ISSN
0362-5915
1557-4644 [online]
Volume/pages
37:4(2012), p. 1-46
Article Reference
25
ISI
000312942400003
Medium
E-only publicatie
Full text (Publisher's DOI)
UAntwerpen
Faculty/Department
Research group
Publication type
Subject
Affiliation
Publications with a UAntwerp address
External links
Web of Science
Record
Identification
Creation 28.02.2013
Last edited 17.08.2017
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