Re: more closed-world chatter

paul c wrote:
> If I have a domain of items consisting of the values "a" and "b" and a
> domain of item prices consisting of the values "1" and "2" and an empty
> relation {ItemID, Price} known by the relvar name "Items", I take it
> that the logical complement of "Items" has four tuples - loosely,
> <a,1>,<a,2>,<b,1>,<b,2>.
>
> If I select from Items where Price = 3, should a dbms answer with an
> empty relation or should it take exception, such as "illegal question"?
> If it doesn't take exception, then I'd guess it is supposing a
> complement that has an infinite number of tuples which couldn't be
> implemented on a finite computer.
>
> As unhappy as this makes me, I'm now thinking exceptions can't be
> avoided in practice.
>
> p
>

Ie., is it a logical mistake to allow the query in the first place?

p Received on Wed May 02 2007 - 22:17:58 CEST