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facts and semantics was: Re: Predicates and Arcs vs Triples

From: Jonathan Borden <jborden@mediaone.net>
Date: Fri, 1 Jun 2001 11:52:47 -0400
Message-ID: <067401c0eab2$e796c570$0a2e249b@nemc.org>
To: "Geoff Chappell" <geoff@sover.net>, "pat hayes" <phayes@ai.uwf.edu>, "Graham Klyne" <GK@NineByNine.org>
Cc: <www-rdf-logic@w3.org>
Geoff Chappell wrote:

> ----- Original Message -----
> From: "Jonathan Borden" <jborden@mediaone.net>

> ...
> > Now suppose I enter a statement to the effect that "everything John says
> is
> > true".
> >
> > The model _does not_ contain a mechanism to unreify the statement _as a
> > statement_ i.e. still does not contain the statement:
> Isn't that because rdf is just the first step/layer? RDF has no mechanisms
> to handle variables, quantification, implications, etc. (and so as a
> knowledge representation language it's not particulary expressive.) But
> wasn't that always the plan? My understanding of the rdf roadmap is that
> will serve as a triple-based data model for storage of facts --

I guess the big problem I see is that RDF defines a _fact_ which seems step
on the toes of semantics (perhaps it plain smashed the toes), and goes on to
define _reification_, which if not stepping on toes is perhaps more like
breaking its ankles.

> with
> reification just a convention to store "preparsed metafacts" that will
> be given meaning by a processor/logic system higher up in the chain (i.e.a
> system might have a rule:  infer {?a ?b ?c} from {say john {?a ?b ?c}}).
> much of the argument/confusion about reification seems to stem from the
> that it's pretty useless without another layer (and the fact that it tries
> to do too much/has overloaded meaning - with bags, etc.).


> Do others see it differently? is rdf trying to become a fully expressive
> knowledge representation language -- a la kif -- in and of itself ?  There
> seems to be so much blurring at times between the rdf triple model, its
> serialization, and the logic layer(s) that act upon it. I worry that if
> those layers aren't kept distinct (at least conceptually) poor decisions
> will be made about where functionality belongs.

I think this is the reason to define an RDF Abstract Syntax which is capable
of representing expressions, and using which expressions can be stored in a
database etc. Onto this should be attached appropriate semantics.

Received on Friday, 1 June 2001 12:09:38 UTC

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