Re: One-To-One Relationships
From: paul c <toledobythesea_at_ooyah.ac>
Date: Fri, 30 Nov 2007 18:46:45 GMT
Message-ID: <pUY3j.8185$UQ1.7708_at_pd7urf1no>
>
> That certainly means you can define them formally in database terms,
> right?
> Here is one such attempt:
> http://arxiv.org/PS_cache/arxiv/pdf/0710/0710.2083v1.pdf
> It defines an entity as a relation (aka table:-) with a single
> noncomposite key, and relationship as a table with composite key. Does
> this definition pretty much exhausts the entity-relationship theory?
>
> (But then BB remark was that order line is a weak entity).
>
>
Date: Fri, 30 Nov 2007 18:46:45 GMT
Message-ID: <pUY3j.8185$UQ1.7708_at_pd7urf1no>
Tegiri Nenashi wrote:
> On Nov 30, 8:19 am, Jan Hidders <hidd..._at_gmail.com> wrote:
> The distinction between entities /
>> relationships, domain objects / predicates is pretty well-established >> in linguistics, philosophy and logic.
>
> That certainly means you can define them formally in database terms,
> right?
> Here is one such attempt:
> http://arxiv.org/PS_cache/arxiv/pdf/0710/0710.2083v1.pdf
> It defines an entity as a relation (aka table:-) with a single
> noncomposite key, and relationship as a table with composite key. Does
> this definition pretty much exhausts the entity-relationship theory?
>
> (But then BB remark was that order line is a weak entity).
>
>
If you are accurate that an entity depends on a relation, then I'd agree ER theory gets exhausted pretty quickly indeed.
Not to encourage the literalists here but an ordinary dictionary definition of entity, eg.,
"The existence of something considered apart from its properties."
suggests even more directly how superfluous ER modeling is. Received on Fri Nov 30 2007 - 19:46:45 CET