SUO: Reification
I wrote:
> On Sun, Apr 07, 2002 at 02:00:09PM +0200, Jean-Luc Delatre wrote:
> > The RDF people are struggling with "reification" because they do not
> > want to recognise that, in many cases, it amounts to high order statements.
> > Trying to hide that results in incredibly contrived definitions which
> > make it *even more* difficult to find one's way toward some solution.
>
> I guess you are referring to the fact that RDF(S) involves reference to,
> and perhaps quantification over, properties. That, in and of itself,
> does not make a language higher-order. I'd suggest you have a look at
> Pat Hayes' model theory for RDF(S): http://www.w3.org/TR/rdf-mt. You
> might also consult the definition of "higher-order" in some standard
> logic text.
Bill Andersen informs me that "reification" indicates reference to, and
perhaps quantification over, propositions. But exactly the same point
applies. Including propositions in one's semantic domain does not in
and of itself make a language higher-order. (Indeed, there doesn't even
exist a semantic notion of proposition in standard higher-order logic.)
-chris