Re: Identity modelling

From: Marshall Spight <marshall.spight_at_gmail.com>
Date: 31 Aug 2005 21:45:22 -0700
Message-ID: <1125549922.227961.176370_at_g47g2000cwa.googlegroups.com>


dawn wrote:
> Marshall Spight wrote:
>
> > I am trying to highlight the significance of
> > content based addressing. It's not just another kind of pointer.
> > It's different.
>
> So if an instance cannot exist without a value for the identifier, then
> it is a key, otherwise a value that uniquely identifies it would be a
> pointer -- is that close?

Yes! That's close.

> > Yes, because the web doesn't used content-addressable storage.
> > Yes, because URLs are pointers.
>
> Are they pointers with the same meaning used by Codd in his earlier
> treatments of relational theory? (I'm not looking it up now, so
> perhaps it is, but that was not my impression)

Strangely, I've never read Codd, so I can't comment.

> > > Maybe we should just say that the URL is a key, but not a relational
> > > key to the web page?
> >
> > You are of course free to call it that. I'm going to call it a pointer
> > to the web page.
>
> I was happy calling foreign keys pointers until I was corrected on
> that, but perhaps this will give me more clues to what can be called a
> pointer. I figured a foreign key was a pointer because it was not part
> of the entity to which it was pointing. Does that work with your
> definition?

I suppose one can use a term in a strict way, or in a general way. If one is not being strict, one could call a foreign key a pointer, but then a valuable distinction is lost. (Which might be okay in context.)

Marshall Received on Thu Sep 01 2005 - 06:45:22 CEST

Original text of this message