Re: c.d.theory glossary - RELATION

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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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