Re: One-To-One Relationships

Marshall wrote:

> On Dec 1, 8:52 am, rp..._at_pcwin518.campus.tue.nl (rpost) wrote:
>

>>>Entities are figments of our imaginations.
>>
>>Heh.  So are relations, attributes, values, and domains.
>>So are rectangles, straight lines, points, and angles.
>>So are "real" numbers, functions, and differential equations.
>>But they all work pretty well.

We do not pretend that relations are real or are part of the universe of discourse -- with the notable exception of the system catalog, of course. Relations make no imagined and unecessary distinctions. They are merely a structure and operations useful for symbolic manipulation.

Fictitious distinctions increase complexity without any compensating benefit.

>>We're dealing with conceptual modelling here.
>>I prefer the term 'modelling constructs', if you don't mind.
>>
>>I agree with Chen (and e.g. OO design, which takes it to another extreme)
>>that a notion of entity is natural, unproblematic and well worth having.
>>
>>You apparently disagree.  Make me understand why.  Be specific.

I already was specific, and the idiot accused me of having a trantrum for my specificity.

> I know you weren't asking me, but my question about the
> whole entities thing is, what do they buy me? I mean,
> I already have this concept of "relation" which seems to
> be powerful enough to be considered a foundation for
> more or less all of mathematics. What *new* capability
> is introduced by having a different thing called "entity?"
>
> Why can't I just write down relations?

Indeed. Or predicates is another good option, which amounts to the same.

> If I don't have them fully modeled yet, I don't see how
> the identity question is any issue. I know every relation
> will have *some* key. If I need to reference a specific
> member of relation B from relation A, I know it will be
> possible to have an attribute in A that is a key of relation
> B. If I just call it BId for the moment, what is the problem?
> If I later discover that B has a compound key, then that's
> fine too.
>
> My end product is a schema for relations. Why don't I just
> model using those? Why not cut out the middle man?
>
> http://dictionary.reference.com/search?q=disintermediation
>
> Marshall
Received on Sat Dec 01 2007 - 23:37:17 CET