correction (was: RE: What do the ontologists want)

A few days ago I replied to Bill deHora:

>I don't know enough to say whether reification itself is a dud for
>RDF. In my KR102 class and in the 2 or 3 books I have that mention
>reification, it came across as a technique to allow a language to
>refer to its categories which are sometimes treated as predicates,
>like dotcom(shop.com), and offers a trick that allows you to say
>titsup(dotcom, shop.com) and treat the predicates as terms in the
>language.

Careful: do you mean predicate symbols, or the predicates themselves 
(ie the properties that the predicate symbols denote)? The way I 
understand it, reification means treating the symbols as objects. If 
you want to refer to a predicate, you just use the predicate symbol 
in the usual way (ie without reifying it.)
What you are talking about here seems to be translating higher-order 
notation into first-order notation by using what KIF calls a 'holds' 
relation, ie you write  holds(R, ?x)  instead of  R(?x) . Which is a 
neat trick, but not reification.

-------

Which was wrong. That *is* reification, in the technical sense where 
to reify something is to treat it as an object, ie admit it into the 
domain of discourse. As Bill pointed out to me, several textbooks use 
the term in this sense for just this usage. However, it is 
reification of a relation (or property), not of a sentence or 
expression. I should have said "that is not the reification that the 
RDF spec refers to".

Sorry for any confusion caused.

Pat Hayes

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Received on Saturday, 19 May 2001 23:57:17 UTC