Re: Reminder, blatant ad

In article <1138380152.680513.293150_at_g49g2000cwa.googlegroups.com>, jog_at_cs.nott.ac.uk says...
> Jan Hidders wrote:
> [snip]
> I do not agree with this. Conventional ordering (and hence listing) is
> mathematically impossible in the relational model period, due to the
> Codd's redefinition of RM-relations and the model's closure.

Can you elaborate on this? I can't immediately see why lists are harder than arrays, special cases of which even today's SQL systems can handle.

> Dawn is
> hence correct imo - lists must be interpreted by a process external to
> the RM, not for the sake of simplicity, or query optimization, but
> rather because the very the nature of that data model precludes their
> implementation.

...though of course if you view the type system as "external to the RM", you are correct---but I don't really see the point of the argument in that case.

-- 
Jon