Re: The horse race

Mark Johnson wrote:
> "JOG" <jog_at_cs.nott.ac.uk> wrote:
>
> >I would avoid this example guys as it centres around the subtle
> >distinction between a mathematical relation and a db-relation.
>
> Then you should define the "subtle distinction" if one is not the
> other.

Sure, but this has been talked about numerous times on here and the onus is on yourself have a look around through the archive. A mathematical relation does not have a 'header' component, a db-relation does. Please refer to date's definitions, and Dawn made an excellent point on her blog discussion about Codd's interpretation of this subject.

>
> Codd spoke of tables, as I understand it. I'm not sure a table
> corresponds to a relation, however.

Not really, he talked about relationships in the form of relations - a table is just a representation. I'm sure you have looked at it, but just in case you have not the best source of course is Codd's original paper, "A relational model for large shared databanks", 1970, Communications of the ACM.

>
> >former ordering of elements within the tuple does matter
>
> Because they are ordered by position.

indeed - I tend to refer to planetmath when online for formal mathematical definitions - it's a good site. However I would say that its worth being 99% of the excellent posters in this group are knowledgeable of these formal definitions, and if it ever appears otherwise, there has probably been a miscommunication.

>
> >and in the latter it does not due to column names
>
> Because they are named, which corresponds to a keyword/value pairing.

indeed each tuple is finite partial map - I would refer you to Jan Hidders previous posts as he comes across extremely knowledgeable in this area.

>
> >i.e. you're both right from a different foundational assumption.
Received on Fri Feb 24 2006 - 01:37:44 CET