Re: One-To-One Relationships
Date: Fri, 30 Nov 2007 08:19:34 -0800 (PST)
On 29 nov, 23:16, JOG <j..._at_cs.nott.ac.uk> wrote:
> On Nov 28, 8:43 pm, rp..._at_pcwin518.campus.tue.nl (rpost) wrote:
> > paul c wrote:
> > [...]
> > >Regarding ER, here are some quotes from Codd's book (available for free
> > >at acm.org). The sarcasm of the second one made me laugh.
> > The criticisms you quote may be amusing, and they have merit, but
> > they ultimately miss the point. The distinction between entities and
> > relationships: entities have identity (they can be referred to; attributes
> > can have entity-valued domains), while relationships do not (they are
> > completely identified by their, possibly entity-valued, attributes).
> I realise that others have attempted to point out your mistakes, but I
> just wanted to echo their sentiment.
How about providing some real arguments, in stead of just sentiments? Haven't seen much of those here and I think Reinier deserves them.
> There is absolutely no difference
> between an entity and a relationship. E/R modelling has /itself/
> conceded this, translating relationships into "associative entities".
Ah, yes, and as we all know, if two concepts have overlap then they are actually the same. *sigh* The distinction between entities / relationships, domain objects / predicates is pretty well-established in linguistics, philosophy and logic. First-order logic, you may have heard of it, separates them even strictly. Are you now going to claim that it is no good for reasoning?
- Jan Hidders