Can we use the universal instance assumption without using nulls?

Yehoshua Sagiv*

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

71 Scopus citations

Abstract

We claim that the representative instance of [Ho1, Va3] is a correct representation of the data stored in a database even when the relations of the database are not the projections of a single universal instance. If no constraint (other than functional and join dependencies) is imposed on the data, then projections of the representative instance cannot always be computed by lossless joins. We show that if the database satisfies a modified foreign-key constraint, then projections of the representative instance can be computed by performing the union of several lossless joins. A class of relation schemes for which no constraint is necessary is characterized, and we show how to compute projections of the representative instance for databases that belong to this class.

Original languageEnglish
Title of host publicationProceedings of the 1981 ACM SIGMOD International Conference on Management of Data, SIGMOD 1981
PublisherAssociation for Computing Machinery
Pages108-120
Number of pages13
ISBN (Print)0897910400
DOIs
StatePublished - 29 Apr 1981
Externally publishedYes
Event1981 ACM SIGMOD International Conference on Management of Data, SIGMOD 1981 - Ann Arbor, United States
Duration: 29 Apr 19811 May 1981

Publication series

NameProceedings of the ACM SIGMOD International Conference on Management of Data
ISSN (Print)0730-8078

Conference

Conference1981 ACM SIGMOD International Conference on Management of Data, SIGMOD 1981
Country/TerritoryUnited States
CityAnn Arbor
Period29/04/811/05/81

Bibliographical note

Publisher Copyright:
© 1981 ACM.

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