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Re: Smart Database Tricks

From: David Cressey <cressey73_at_verizon.net>
Date: Fri, 22 Jun 2007 14:45:28 GMT
Message-ID: <cgRei.3$t95.0@trndny01>

"Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message news:467bbfa9$0$4321$9a566e8b_at_news.aliant.net...
> Jan Hidders wrote:
> > On 22 jun, 01:36, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> >
> >>Jan Hidders wrote:
> >>
> >>>On 21 jun, 21:17, vldm10 <vld..._at_yahoo.com> wrote:
> >>
> >>>>On Jun 18, 7:41 pm, Jan Hidders <hidd..._at_gmail.com> wrote:
> >>
> >>>>>On 18 jun, 20:59, vldm10 <vld..._at_yahoo.com> wrote:
> >>
> >>[snip]
> >>
> >>
> >>>>>If this is a relation then
> >>>>>all columns are attributes and since you have represented all the
> >>
> >>>>Can you please, tell me what is the definition of the attribute in RM.
> >>
> >>>It's a column of a relation. Conceptually it represent the role in the
> >>>predicate that is represented by the relation.
> >>
> >>Is an attribute a predicate variable of some sort?
> >
> > As in "the x in predicate P(x, y) "? Yes, I'd say that is the same
> > thing.

>

> I thought so. When one writes a query and requests certain attributes,
> would those requested attributes be free variables in a logic sense?
>

> When one uses an attribute in a restrict condition or join condition,
> would that attribute be a bound variable in a logic sense?

I don't know what the term "free variable" means in the world of logic. I do know what it means in the context of Lisp programming. (Or, at least, I used to know). So far, the use of "free variable" in these discussions seems to be consistent with the Lisp usage. Received on Fri Jun 22 2007 - 09:45:28 CDT

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