Re: Constraints and Functional Dependencies

On Feb 24, 12:47 pm, "Walt" <wami..._at_verizon.net> wrote:
> "Marshall" <marshall.spi..._at_gmail.com> wrote in message
>
> > In a data management context, there is some value to restricting
> > what we can quantify over as being only attributes of declared
> > relations (whether variables or constants.) So, we can't express
> > the "no-upper-bound" property of the natural numbers; they aren't
> > a database table so we can't quantify over them.
>
> > With such a system, a relation R with attribute a (which I will
> > write as R(a)) having a as a foreign key into S(b) is expressed
> > as follows:
>
> > forall R(a): exists S(b): a = b
>
> Nitpicking response: the above not only expresses the foreign key concept,
> but also referential integrity.
> I don't want to make a mountain out of a mole hill here. I just want to
> reach consensus, if possible, before considering the rest of your
> discussion.

Reviewing a variety of definitions, it seems to me that what I wrote above would best be called "referential integrity" and not a "foreign key" per se, since I haven't specified any keys.

http://www.google.com/search?q=define%3Areferential+integrity

Thank you for pointing that out. (Seriously.)

Marshall Received on Sun Feb 25 2007 - 06:29:12 CET