Re: One-To-One Relationships

"Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message news:4752d39e$0$5266$9a566e8b_at_news.aliant.net...
> David Cressey wrote:
>
> > "Cimode" <cimode_at_hotmail.com> wrote in message
> >
news:36f20483-5085-4d52-b33d-1ddd85bd6735_at_w56g2000hsf.googlegroups.com...
> >
> >>On 30 nov, 19:33, JOG <j..._at_cs.nott.ac.uk> wrote:
> >>
> >>>On Nov 30, 6:03 pm, Tegiri Nenashi <TegiriNena..._at_gmail.com> 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?
> >>>
> >>>I like the insight that both 'entities' and 'relationships' are
> >>>subtypes of a parent concept, that is simply a set of attributes and
> >>>values. I'd like to see a formalization of that which doesn't rely on
> >>>relational theory and the concept of keys however, even though I
> >>>imagine there would be a direct correspondence.
> >>
> >>OK I will play devil's advocate and try to believe that entities could
> >>be an alternative expression of entities...
> >>
> >>Quite frankly, I understand the intent but not the need to
> >>differentiate relations and entities...
> >>
> >>I believe somehow that because Relations rely on set theory and
> >>relational algebra, it simply has a longer mathematical history and de
> >>facto more abstract tools concepts to work with than Entities that
> >>seem recent. I do believe that the keys was simply Codd's way to
> >>express *identifiablity* in a way that his IBM audience could be
> >>receptive to the rest of the model...I do not perceive keys as a
> >>sufficient reason to require differentiation between the two models...
> >
> > Entities are not recent. Entities are as old as Aristotle. Aristotle
was
> > not attempting to design databases. Codd was not attempting to
reformulate
> > the metaphysics of how we understand reality.
> >
> > Chen's contribution was to provide a model in which the information
> > requirements can be stated without presupposing a design that is going
to
> > meet those requirments.
>
> In exactly what ways did Chen's contribution improve over the previously
> existing conceptual analysis techniques?

What are the previously existing conceptual analysis techniques? Received on Sun Dec 02 2007 - 19:26:52 CET