Re: A Logical Model for Lists as Relations

Jay Dee wrote:
> Bob Badour wrote:
> > Since it is relatively easy to write a query that extends a relation
> > with a rank per any explicit order, I am not even sure the ordinal
> > attribute is required.
>
> True. I wasn't exactly sure what MS wanted to happen, for example,
> to the fourth element in a list when the second element is elided.
> Does it become the third? If so, your proposal is a good
> solution. But...
>
> What if he envisions a list in which duplication of elements is
> significant?

If one has a numeric index that differs for each tuple, one never has duplication. If one has duplication, one wonders how to refer to the duplicates. As Codd observed long ago, once one has said a thing is true, what does saying it again achieve?

   In that case - and I'm supposing that's what MS
> had in mind - a relation of element values wouldn't work.
>
> "More requirements, please!"
>
> In the end, though, I'm confident that the lists MS desires can be
> implemented in a relational design without inventing anything beyond
> what already exists.

I still do not know what sort of requirements would cause me to want a list in the first place. Received on Thu May 11 2006 - 01:24:52 CEST