# Re: c.d.theory glossary - RELATION

From: x <x-false_at_yahoo.com>

Date: Mon, 26 Apr 2004 17:27:27 +0300

Message-ID: <408d1ba2$1_at_post.usenet.com>

Date: Mon, 26 Apr 2004 17:27:27 +0300

Message-ID: <408d1ba2$1_at_post.usenet.com>

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"Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message
news:c6j2ge$ket$1_at_news.netins.net...

> Relation:

*>
**> A relation is a subset of the set of ORDERED tuples (A1, A2, ... Am)
*

formed

> by the Cartesian cross-product of sets S1 x ... x Sm where each An is an

*> element of Sn.
*

Codd made a distinction between a RELATION and a RELATIONSHIP.
In Math a RELATION is what you described.
In relational model, many would work with a RELATIONSHIP instead.
A RELATIONSHIP is similar to a RELATION

A RELATIONSHIP is a subset of the set of UNORDERED tuples
{"S1":A1,"S2":A2,...,"Sm":Am}

where each An is an element of Sn and "Sn" is the name of the set Sn.

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