Re: Notions of Type

paul c wrote:
> Aloha Kakuikanu wrote:
> > Keith H Duggar wrote:
> >> Marshall wrote:
> >>> Very true. Of the various relational operators that have
> >>> been identified over the years, only a few, like union,
> >>> are really algebraic.
> >
> > Except that union applies to relations of the same arity only.
>
> I thought that was only a practical restriction, ie., in theory, any
> relations can be unioned?

Which theory:-?

In classic RA they aren't.

In D&D algebra they are. In relational lattice they are too. Received on Fri Aug 18 2006 - 02:11:17 CEST