Re: Objects and Relations

On Feb 15, 12:22 am, "JOG" <j..._at_cs.nott.ac.uk> wrote:
> On 14 Feb, 13:12, "Cimode" <cim..._at_hotmail.com> wrote:

[snip]

> > > 2) Hence their x,y,z position attribute always identifies them.
>
> > False.
>
> Location always identifies something. Two things cannot be in the same
> place. It's sort of a law of physics, and I've got to be honest,
> knowing it has tended to help me in daily life. Like if my tv is in
> the corner of the room my car probably isn't there too.

A quibble: saying "Location always identifies something" doesn't seem quite right. Not all things are physical things. For example location doesn't identity a company like Coca Cola. Furthermore some physical things aren't particularly well localised in space. Eg a railway line.

Also, spatial location won't be adequate in a temporal DB. I presume you would then say that (x,y,z,t) identifies the thing. Would you be prepared to introduce a surrogate id that stands for (x,y,z,t), so that nothing keeps its identity from one moment to the next?

Consider this example: There is a box containing a number of macroscopic particles. We use stereoscopic vision for a device that is able to record (x,y,z,t) of each particle. Over time we build up sampled data and record all measurements in a single relation. Are you happy to say that (x,y,z,t) (or else a surrogate standing for (x,y,z,t)) is the key and the particles as entities is illusionary?

Curiously in QM exchange symmetry of the wave function is required for identical particles. However for macroscopic particles like above I would say their identity is "real" even though a suitable identifier must be invented in the sense of a surrogate id. I agree with the pov that all identifiers are merely names and whether you call them natural or surrogate isn't particularly interesting.

I am struggling with your assertion that relations only are about roles and values, not entities. You have yet to provide an explanation. I have the impression that you think in terms of entities but aren't prepared to admit it. Take for example your words like "something", "item" etc

[snip] Received on Thu Feb 15 2007 - 03:24:07 CET