W3C home > Mailing lists > Public > www-rdf-logic@w3.org > July 2002

Re: Paradoxes are bugs on the SW was: Re: questions on assertion

From: Giles Hogben <giles.hogben@jrc.it>
Date: Tue, 9 Jul 2002 14:57:31 +0200
Message-ID: <019001c22748$2fbab910$162abf8b@pcdsa22>
To: "Jonathan Borden" <jonathan@openhealth.org>, "Joshua Allen" <joshuaa@microsoft.com>, <www-rdf-logic@w3.org>

So what is the meaning of assertion in RDF? If triples are, as you say,
unasserted, what is the meaning of

"This document describes a model theory for RDF(S) which treats the language
as simple assertional language, in which each triple makes a distinct
assertion and the meaning of any triple is not changed by adding other
triples"

----- Original Message -----
From: "Jonathan Borden" <jonathan@openhealth.org>
To: "Joshua Allen" <joshuaa@microsoft.com>; "Giles Hogben"
<giles.hogben@jrc.it>; <www-rdf-logic@w3.org>
Sent: Tuesday, July 09, 2002 2:32 PM
Subject: Paradoxes are bugs on the SW was: Re: questions on assertion


> Joshua Allen wrote:
>
> >
> > You are right about the incorrect syntax, thanks.  Also, I agree that
> "veracity" is something outside of RDF, just like "color".  The point
being
> that "veracity" is something to be asserted, judged, and weighed; and a
> web-based system must be able to accept or reject assertions.  Given that,
I
> see no problem with the example below -- it is clearly contradictory and
> useless, but I don't see a problem with that -- you will be sure to get
lots
> of contradictory and useless assertions mixed in with the good stuff in
any
> web-based system.  (But maybe I am missing some things?)
> >
> > <rdf:Description rdf:about="#Statement1">
> >     <ex:Veracity rdf:ID="Statement1">False</ex:Veracity>
> > </rdf:Description>
>
> In RDF, the way RDF uses the term "assertion" according to the RDF Model
> Theory, there is no problem with the above statement. The "ex:Veracity"
> predicate has no effect on the truth value (or assertional 'status') of
the
> statement: all statements in RDF are asserted, plain and simple.
>
> RDF has no negation, by design. You may not like that, you may holler, you
> may protest that the web _must_ have negation, but RDF is not going to
give
> it to you. Some argue this is a draconian design decision, but for the
> Semantic Web to work as intended, we need to avoid logical paradoxes
> (contradictions are simple to deal with: "(A and not A)" is simply false).
> The design of RDF avoids some common paradoxes by not providing negation,
> plain and simple.
>
> Issues like trust and belief have been placed higher on the SW "layer
cake"
> and it is the intention of _other_ languages (presumably built on RDF but
> perhaps not) to deal with such issues.
>
> These exact issues -- for example suppose a higher level language _wants
to_
> introduce negation, but needs to avoid a paradox when RDF asserts the
> statement it is trying to negate -- these very issues are at the heart of
> the "layering" debate that has gone on in the WebOnt WG archives.
>
> The idea of "unasserted triples" allows a "higher level" language to
define
> the truth value for such triples according to its own rules (i.e. model
> theory).
>
> On the other hand you need to realize the importance of avoiding logical
> paradoxes at all cost, for the Semantic Web, because -- a logical paradox
is
> the logic equivalent to a "buffer overflow" in a Web server, etc. that is
> potentially attached to your bank account -- the point being that if I as
a
> human am going to trust some Bot that I've sent out to do my shopping, I
am
> not going to tolerate a paradox which would be capable of convincing my
Bot
> that the Brooklyn bridge is actually the red shirt I want to buy in which
> case I would buy the Brooklyn bridge ... but it wouldn't be the Brooklyn
> bridge because it would be a red shirt ... but it would be the Brooklyn
> bridge because ...
>
> Jonathan
>
Received on Tuesday, 9 July 2002 08:53:14 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:52:42 GMT