Re: Towards a definition of atomic

From: David Cressey <>
Date: Fri, 01 Feb 2008 15:36:34 GMT
Message-ID: <60Hoj.3$k%2.2_at_trndny09>

"Roy Hann" <specially_at_processed.almost.meat> wrote in message
> "David Cressey" <> wrote in message
> news:wOFoj.5441$4f.724_at_trndny06...
> >
> >> I think we could make the meaning of "atomic" more tangible if we can
> >> define what decompositions of an attribute are valid.
> >
> > Perhaps the place to start is to define what kinds of compositions a
> > relational system is capable of. Once you have that in place, it
> > be
> > straightforward to define relational decompositions as the inverse of
> > relational compositions.
> Why not just understand that relational systems don't care about about
> composition/decomposition and want nothing to do with the idea? It is no
> more relevant than is the concept of colour to Euclidean geometry.
> Roy

I disagree. A relation is composed of attributes. (If you prefer, a table is composed of columns). Relational systems are clearly concerned with composition in some contexts.
One of the relational operators discussed is the "compose" operator, by which a result relation can be composed from given relations. (If you prefer, a result table can be composed from given tables (or views)). Received on Fri Feb 01 2008 - 16:36:34 CET

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