Re: MV Keys

From: David Cressey <dcressey_at_verizon.net>
Date: Tue, 07 Mar 2006 14:02:39 GMT
Message-ID: <3ogPf.3025$zp2.2327@trndny01>

"Marshall Spight" <marshall.spight_at_gmail.com> wrote in message news:1141720100.794765.5770_at_e56g2000cwe.googlegroups.com...
> Jon Heggland wrote:
> > marshall.spight_at_gmail.com says...
> > >
> > > But isn't a tuple a subtype of a relation?
> >
> > Not according to the definitions I prefer. I feel uncomfortable with the
> > circularity this would entail: That a relation is a set of relations(?).
>
> Relation: a subset of a product of sets
> Tuple: a subset of cardinality 1 of a product of sets.
>
> Seems like a subtype to me. Every place a relation value
> could be used, a tuple value could be used instead.
>
> Note there is no circularity required.

This is like x's question, phrased differently

suppose you evaluate

e == [e]

Does this evaluate to true?
does it evaluate to false?
does it evaluate to something else?
does it generate a run time exception (type mismatch)? Does it generate a compile time exception (type mismatch)? Received on Tue Mar 07 2006 - 08:02:39 CST