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Home -> Community -> Usenet -> comp.databases.theory -> Re: Negative Numbers in "Identity" or" Autonumber" fields

Re: Negative Numbers in "Identity" or" Autonumber" fields

From: David Cressey <cressey73_at_verizon.net>
Date: Wed, 21 Mar 2007 14:26:13 GMT
Message-ID: <9gbMh.13363$dG.12145@trndny08>

"JOG" <jog_at_cs.nott.ac.uk> wrote in message news:1174483996.150218.17240_at_l75g2000hse.googlegroups.com...
> On Mar 21, 6:46 am, "Marshall" <marshall.spi..._at_gmail.com> wrote:
> > On Mar 20, 10:31 am, "JOG" <j..._at_cs.nott.ac.uk> wrote:
> >
> >
> >
> > > [...] Nothing in a
> > > proposition should ever be hidden from the user. Propositions come
> > > from outside of the logical layer after all. If an attribute is an
> > > identifier then it clearly impacts on identifying items in the real
> > > world.
> >
> > I buy the "nothing should be hidden" argument, but I can't
> > decide if a domain that only supports equality is hiding
> > anything or not.
> >
> > Marshall
>
>

Marshall,

I also want to know what "only supports equality" means. I assume you mean that the theta operator "is equal to" yields results consistent with the identtity of the entity the domain is acting as a surrogate key for.

"is equal to" could yield a false positive is there a homonyms in the domain of the surrogate. (Meaning that two different entities somehow end up with the same surrogate key). And "is equal to" could yield a false negative if there are synonyms (meaning that a single entity gets assigned two different surrogates).

However, the word "only" in your post means something like "less than" conveys no information.
This is not the case for the numbers one takes for service at the deli counter. If they say "now serving 72" and my number is 73, that tells me something. Or am I misreading you. Received on Wed Mar 21 2007 - 09:26:13 CDT

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