Re: Objects and Relations

Walt wrote:

> "JOG" <jog_at_cs.nott.ac.uk> wrote in message
> news:1172092159.136958.258750_at_m58g2000cwm.googlegroups.com...
>

[justification for pretty pictures snipped]

The word "relationship" for "association" ias a little more
> troublesome. In the RM, "relation" is used for mathematical relations
> which are thought of, outside the area of data management, as ordered
> tuples. "relationship" is a word that is used in the RM to describe
> something very much like a relation, except that the components of the
> tuples are referenced by name, and not by position.
>
> I'm so accustomed to thinking in terms of tables with rows and columns,
> that I almost never make the distinction between a "relation" and a
> "relationship", except in discussions like this one.

I realise Codd made that distinction when first introducing his notation in the 1970 paper. I don't find it a useful distinction, and I am unaware of anyone using it since. Different notations are simply different representations of the same 'thing': a relation.

[more snippage]

> It took me a long time to come to this view. When I first saw ERM, I
> thought of it as "RM lite". That's not the best way to use it. The best
> way to use it is to distinguish between data analysis (ERM), and abstract
> (logical?) database design, (RM).
>
> Just my two cents.

ERM is not lite. ERM is very heavy with hallucinated distinctions. Received on Thu Feb 22 2007 - 15:35:53 CET