Re: One-To-One Relationships
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Sun, 02 Dec 2007 11:47:38 -0400
Message-ID: <4752d39e$0$5266$9a566e8b_at_news.aliant.net>
>
> well-established
>
>
> attempt:http://arxiv.org/PS_cache/arxiv/pdf/0710/0710.2083v1.pdf
>
>
> 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.
Date: Sun, 02 Dec 2007 11:47:38 -0400
Message-ID: <4752d39e$0$5266$9a566e8b_at_news.aliant.net>
David Cressey wrote:
> 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? Received on Sun Dec 02 2007 - 16:47:38 CET