Re: Relation Schemata vs. Relation Variables

vc wrote:
> Jan Hidders wrote:
> [...]
> >. Note btw. that they are a strict
> > subclass of the restrictions that might be expressed by some kind of
> > temporal logic.
>
> What temporal logic do you have in mind ?

First order logic extended with the 'since', 'until', 'next' and 'previous' operators.

> It's known that first-order
> temporal logic is strictly less expressive than FOL for a relational
> database augmented in a natural way with a timestamp column, or in
> other words FOTL is less expressive than two sorted FOL with the time
> domain as an additional sort ( the propositional fragments of both are
> equivalent).

Indeed, even if you extend it with temporal operators for all regular expressions, but that is not what I was comparing it to.

• Jan Hidders