Re: Codd's Information Principle
Date: Thu, 5 Nov 2009 15:08:53 -0800 (PST)
Message-ID: <fa2bfdde-6463-49d2-8f07-dee707b63bd9_at_m35g2000vbi.googlegroups.com>
On 5 nov, 20:09, paul c <toledobythe..._at_oohay.ac> wrote:
> Cimode wrote:
> > ...
> > I would be glad to hear how we establish a valid quantifier in
> > relational algebra using only internal predicates. ...
>
> I thought projection is relational algebra's quantifier, are you talking
> about something else?
Not sure...
The concept that a relational *operation* (projection) involving a relation R1 would also serve as a quantifier for the same relation is a concept I am having difficulties with.
I'd rather have quantifiers defined according to a domain subtyping (knowing that each un-ary relation attribute is nothing else a domain subtype associated with both a header and additional relation level constraints). I found that such approach is more practical to establish quantifiers through the use of domain intervals in relationship to cardinality through combinatory analysis. Received on Fri Nov 06 2009 - 00:08:53 CET