Re: One-To-One Relationships

On Nov 30, 10:53 am, JOG <j...@xxxxxxxxxxxxx> wrote:
On Nov 30, 12:53 am, David BL <davi...@xxxxxxxxxxxx> wrote:





On Nov 30, 7:34 am, JOG <j...@xxxxxxxxxxxxx> wrote:

On Nov 28, 10:37 pm, paul c <toledobythe...@xxxxxxxx> wrote:

Bob Badour wrote:
rpost wrote:
...
This is the exact problem Chen identified. In the relational model
it is impossible to have entity-valued attributes, which, in practice,
we have a huge amount of.

Entities are figments of our imaginations.
...

That's much better than my reply, looks like the essential point to me.

Entities are concepts that we impose on that which is there (mostly
shapes made out of atoms, but sometimes abstractions too).

Entities are 'real' in that they are patterns that we think up and
apply, and 'not real' in that if we were all dead, well there wouldn't
be any 'entities' would there. Just atoms again.

Is this merely an argument against mathematical realism or something
more specific?

I haven't argued anything, I have just defined entities. All seems
like common sense to me.

Suppose I define a bijective mapping called "f" between the integers
{1,2,3} and particular groups of atoms that I perceive right now on my
desk as follows

1 <--> {set of atoms that looks like a pen}
2 <--> {set of atoms that looks like a mug}
3 <--> {set of atoms that looks like a keyboard}

Does this mapping only exist in my mind, and would cease to exist if I
died, or does the mapping have an independent existence? This is
merely a philosophical question about mathematical realism. Or are
you saying that the problem is in a precise definition of the groups
of atoms?

Because we conjure them up 'entities' aren't neatly defined, can
overlap, change, and will differ from person to person. In fact its a
testament to the amazing flexibilty of our noggins that that we
manage to communicate at all.

Do you consider all mathematics to be "conjured up" and therefore not
neatly defined as well?

Non-sequitur. I have made no comments on mathematics nor on anything
being ill-defined.

You made the statement

"Because we conjure them up 'entities' aren't neatly defined"

The use of the word "because" seems to suggest

"conjured up" implies "not neatly defined".

What I am suggesting is that given the contextual nature of how we
define any given entity, any model centered upon them is going to have
a very inflexible, brittle view of the world.

How do you distinguish between a model centered upon entities versus a
model that is not?

There are a load of atoms. Someone else looks at them and says hey its
a dead bit of wood, its a 'stump' entity. Someone else considers a
bigger picture and says its a snapshot of a 'tree' entity. Me, being
lazy, say hey I could sit on that, its a 'seat' entity, etc., ad
infinitum.

Whos right? Noone. Everyone. Who cares. It just depends on the
context, and with shared data, thats gonna vary. So lets encode the
underlying bloody information, and not whatever brittle view of the
world that first pops into our heads, ending up with a brittle,
creaking database.

This appears to be a different argument to your previous one. I think
you are now stating the underlying problem with entities is non-
uniqueness, which I find more agreeable than your previous meta-
physical statements concerning existence.

Or do you consider the non-uniqueness problem to only be a symptom of
your meta-physical standpoint?

And as such, anyone who tells you that you can build a permanent, all
encompassing model out of such utterly woolly things is not to be
trusted as far as you can throw them.

P.S I have also had similar experinces at Ikea :) I don't follow the
arrows anymore. They lie.

If there is a valid argument against "entities" I would hope it can be
stated more carefully than your or Bob's attempts.

Again I haven't argued against entities. However, I am of course
interested in what you deem invalid in my comments.

Yes, you argued against models that are centered around entities.
However I don't actually know what that means.

Please don't take my post in the wrong way. I'm hoping the outcome
will be a more accurate way of saying what's wrong with ER
diagrams! :)


.

Relevant Pages

  • Re: One-To-One Relationships
    ... Just atoms again. ... Does this mapping only exist in my mind, and would cease to exist if I ... fixed and brittle viewpoint of the world. ... model from a neutral underlying logical model. ...
    (comp.databases.theory)
  • Re: One-To-One Relationships
    ... Just atoms again. ... brittle view of the world. ... I thought it was careful and quite ... Entities are subjective and products more of applied psychology than ...
    (comp.databases.theory)
  • Re: One-To-One Relationships
    ... Just atoms again. ... mathematical constructs as having an independent existence. ... fixed and brittle viewpoint of the world. ... uniqueness, which I find more agreeable than your previous meta- ...
    (comp.databases.theory)