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Re: Little question for RDM theoristes

From: J M Davitt <jdavitt_at_aeneas.net>
Date: Fri, 16 Jun 2006 16:23:34 GMT
Message-ID: <aWAkg.60189$mh.21661@tornado.ohiordc.rr.com>


Erwin wrote:

>>Your question implies relations = relvalues...which if I follow this
>>false premise reasonning would lead to relations that have similar
>>relvalues being equal which is totally false...2 relvar with same
>>relvalues are NOT necessarily equal.

>
>
> TTM Chapter 4, RM prescription 10 :
>
> "A relation value (relation for short) ..."
>
> Therefore at least to Chris Date, 'relations=relvalues' is most
> certainly true. I'd say that's a strong indication of just how much
> "false premise" there is within.

CJD is careful to point out that, in certain contexts - especially colloquial, "relation" is used to mean "relation value." But he also points out that

   ...we have these two different concepts, relation value and    relation variable. The trouble is that the literature has    historically used the same term, /relation/, to stand for    both...

   ...I'll distinguish very carefully between the two terms...

   ...I'll also abbreviate /relation value/ most of the time    to just /relation/ ... I'll abbreviate /relation variable/    most of the time to just /relvar/...

I'm not at all familiar with the use of "relvalue."

>>This question is totally irrelevant if you consider a relation as being
>>equal to a relvalue...

>
>
> This question is not irrelevant at all since the heading is regarded as
> the definition of the applicable relation type. And for values to be
> equal, they must most certainly be of the exact same type, inheritance
> issues notwithstanding of course.
>
Received on Fri Jun 16 2006 - 11:23:34 CDT

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