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Information Systems
Volume 23, Issue 7, November 1998, Pages 509-516
 
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doi:10.1016/S0306-4379(98)00025-8    How to Cite or Link Using DOI (Opens New Window)
Copyright © 1998 Published by Elsevier Science Ltd.

Technical note

Minimal lossless decompositions and some normal forms between 4NF and PJ/NF*1

Ragnar Normann

Department of Informatics, University of Oslo, P.B. 1080 Blindem, N-0316, Oslo, Norway

Received 3 August 1997; 
revised 29 May 1998. 
Available online 12 February 1999.

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Abstract

Two popular textbooks in relational database theory are shown to have the same ‘erroneous’ definition of the project-join normal form (PJ/NF) (‘erroneous’ in the sense that their definition is obviously not what the authors intend). A seemingly natural way to rephrase this definition is to introduce the concept minimal lossless decompositions. This concept is shown to yield a countable family of normal forms lying strictly between 4NF and Fagin's original PJ/NF. It also gives an upper bound on the complexity of join dependencies.

Author Keywords: Normalisation; Lossless Decomposition; Normal Form

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Information Systems
Volume 23, Issue 7, November 1998, Pages 509-516
 
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