Re: Is relational theory irrelevant? (was Re: Dreaming About Redesigning SQL)

"Paul" <pbrazier_at_cosmos-uk.co.uk> wrote in message news:51d64140.0311130156.6c376b59_at_posting.google.com...
> "Mikito Harakiri" <mikharakiri_at_iahu.com> wrote in message
news:<DxBsb.30$1n1.179_at_news.oracle.com>...
> > > Ordered domains do have logical order. Relations have no order, but
the
> > > values in the relations have order.
> >
> > That totally depends whom you ask, of course. A person with mathematical
> > background would have no trouble defining an order relation among the
tuples
> > of the original relation induced by the order defined on each domain
> > associated with individual column.
>
> I think the answer is due to the intended "real-life" meaning of
> relations.
> Clearly in general a set can have an ordering defined on it.
> But a relation isn't just any old set, it is a set of *logical
> propositions*.
> So:
>
> 1) the grass is green.
> 2) the sky is blue.
>
> means exactly the same as:
>
> 1) the sky is blue.
> 2) the grass is green.
>
> i.e. P1 AND P2 = P2 AND P1
>
> where P1, P2 are the propositions above.
> So you could say the fact that relations can't have an order comes
> down to the commutativity of the logical AND operator.

What about numbers that you have in front of your propositions? When I ask a list of propositions returned as a result of my query, I would like to have an extra column that has integers numbers in it. Those numbers have to be calculated from the values in the "symantically valid columns". SQL with analytical extensions (window functions) generates such enumerating column easily. How about other languages: RA, RC, Datalog, and D4? Received on Thu Nov 13 2003 - 17:28:29 CET