Re: Objects and Relations

From: David BL <>
Date: 1 Feb 2007 00:37:48 -0800
Message-ID: <>

On Feb 1, 4:04 pm, "Marshall" <> wrote:
> On Jan 31, 1:29 am, "David BL" <> wrote:
> > On Jan 31, 4:10 pm, "Marshall" <> wrote:


> > > Join of two one-attribute relations on their single attributes is
> > > set intersection, which I hope you will agree is a meaningful
> > > and useful operator.
> > I'm not suggesting that there is a problem. I'm trying to say
> > (perhaps badly) that if you model strings relationally you don't
> > suddenly get a whole bunch of simple select-project-join queries
> > across multiple relations that give you useful results. I'm
> > contrasting this with more conventional applications of RM where even
> > simple queries give all sorts of useful information.
> Um, but isn't the number of different possible, joins say, a
> function of the number of attributes? So we shouldn't be
> surprised that relations with fewer attributes have fewer
> possible joins.

Yes. However it seems to me that the fact that you're willing to use nested relations for strings reveals that you don't expect a string relation to join usefully with the other relations. Does that willingness to isolate the relation indicate something?

In my OP for this thread I distinguished between entities that are part of the abstract computational machine, and external entities. Do you agree that the distinction is well defined? Note that one of the "fights" on comp.object was over this question.

If the distinction is meaningful, then it seems to follow that you wouldn't want to mix facts about internal entities and facts about external entities at the one level of abstraction.

Is it possible that your willingness to use a nested relation exactly correlates with the distinction between internal and external entities? At the very least I find this to be an interesting conjecture. It makes strong predictions about relational designs.

The conjecture that OO should keep away from storing information about external entities is also powerful. It puts the OO animal in a nice little cage.

It seems a little peculiar to me to store facts about entities that are in fact part of the abstract computational machine. Why would a machine store facts about its own working parts? To me a machine just "is". Now I guess this is a rather weak argument because a machine may be based on logic or set theory. In any case it is an interesting conjecture just in case RM indeed proves to be deficient for constructing computational machines. Curiously RM would be ideal for storing facts about a given computational machine.

[snip] Received on Thu Feb 01 2007 - 09:37:48 CET

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