Re: more closed-world chatter

On May 2, 10:13 pm, paul c <toledobythe..._at_oohay.ac> 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"?
I would like to point out two comments triggered by your question.

A TRDBMS should detect disjoint types are to be determined at compile time. In my perspective, there should be no exception because there should be no execution in the first place. That of course, in a purely empirical perspective.

> 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.
I am not sure about that a unlimited number of tuple intervall can perfectly be expressed by a compiler by a limited number interval.

> As unhappy as this makes me, I'm now thinking exceptions can't be
> avoided in practice.

> p
Received on Thu May 03 2007 - 15:50:19 CEST