Re: Identity modelling
From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Wed, 31 Aug 2005 20:27:45 +0200
Message-ID: <4315f626$0$11062$e4fe514c_at_news.xs4all.nl>
>
>
> Let's try to use RM for this little problem:
> - the URL is a value
> - the content of the resource is a value
> - there is a relation At(URL, Content) where URL is the primary key with
> At(u,c) meaning that at this instant the URL u point to the content c.
>
> So the URL is a key after all. :-)
Date: Wed, 31 Aug 2005 20:27:45 +0200
Message-ID: <4315f626$0$11062$e4fe514c_at_news.xs4all.nl>
x wrote:
> mAsterdam wrote:
>
>>The URL is just an alias for another locator. >>The existence of what is there (at the pointed-at) >>location does not depend on the existence of the URL.
>
>>Real keys do not have things that are existentially >>dependent on them, but my intuition (not checking >>any definitons anywhere) is that primary keys do: >>A tuple (relational value) can only exist /with/ it.
>
> Let's try to use RM for this little problem:
> - the URL is a value
> - the content of the resource is a value
> - there is a relation At(URL, Content) where URL is the primary key with
> At(u,c) meaning that at this instant the URL u point to the content c.
>
> So the URL is a key after all. :-)
Ah yes, I silently went along with the implicit assumption that the content would be remote, that is /outside/ the closed world. If it is within you are right, of course. Received on Wed Aug 31 2005 - 20:27:45 CEST