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Re: questions on assertion

From: Giles Hogben <giles.hogben@jrc.it>
Date: Tue, 9 Jul 2002 10:08:19 +0200
Message-ID: <00f001c2271f$c9a4ded0$162abf8b@pcdsa22>
To: "Joshua Allen" <joshuaa@microsoft.com>, "Jonathan Borden" <jonathan@openhealth.org>, <www-rdf-logic@w3.org>, <www-rdf-interest@w3.org>

But what about this sentence in the RDF model spec (also in the latest
draft)?

"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"

An assertion is traditionally a statement that you believe something to be
true.

> 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>
>
>
> -----Original Message-----
> From: Jonathan Borden [mailto:jonathan@openhealth.org]
> Sent: Mon 7/8/2002 9:15 PM
> To: Joshua Allen; Giles Hogben; www-rdf-logic@w3.org
> Cc:
> Subject: Re: questions on assertion
>
>
>
> Joshua,
>
> >
> > > In this case, I am trying to figure out in that case how the RDF model
> > > theory would cope with expressing the following.
> > >
> > > 1. my car is red
> >
> > <rdf:Description rdf:about="urn:autos:my-car" rdf:ID="Statement1">
> >   <ex:Color>Red</ex:Color>
> > </rdf:Description>
>
> This isn't quite legal RDF syntax, you cannot have both an rdf:about and
> rdf:ID on the same description. Perhaps you want to add the rdf:ID to the
> property?
>
> In any case the triple:
>
> Statement1: <urn:autos:my-car> ex:Color "Red" .
>
>
> >
> >
> > > 3. X is not true.
> >
> > <rdf:Description rdf:about="#Statement1" rdf:ID="Statement3">
> >   <ex:Veracity>False</ex:Veracity>
> > </rdf:Description>
>
> RDF does not provide/allow negation by design. The above is not the same
as
> "X is not true" because "truth" is defined according to the RDF model
> theory -- see: http://www.w3.org/TR/rdf-mt/
>
> i.e.
>
> <#Statement1> ex:Veracity "False" .
>
> Does not have anything to do with _falsehood_ according to the RDF model
> theory. You may have your own model theory which might use RDF triples as
> syntax, and then you might assign your own truth value to the triple, but
> that isn't according to RDF. For example suppose we take what you say at
> face value:
>
> <rdf:Description rdf:about="#Statement1">
>     <ex:Veracity rdf:ID="Statement1">False</ex:Veracity>
> </rdf:Description>
>
> Is Statement1 true or false? well if it is true then it is false, and if
it
> is false then it is true, ... and if we have paradoxes then we can prove
> anything, which would not make for very useful inferences.
>
>
> >
> > > 6. X is an assertion made by P
> >
> > <rdf:Description rdf:about="#Statement1" rdf:ID="Statement6">
> >   <dc:Author>P</dc:Author>
> > </rdf:Description>
>
> Close enough (sort of). This _was_ the intention of the current RDF REC,
but
> again, according to http://www.w3.org/TR/rdf-mt/ this remains unclear.
>
> >
> > > 7. Y is an assertion made by Q
> >
> > <rdf:Description rdf:about="#Statement4" rdf:ID="Statement7">
> >   <dc:Author>Q</dc:Author>
> > </rdf:Description>
> >
> > > 1. If we interpret an assertion to mean "I believe 'my car is red' is
> > > true."
> >
> > More like "Someone asserted that ('my car is red' is true)".
> >
> > > "I believe ["I believe 'my car is red' is true"] is false"
> > > Which is a paradox.
> >
> > Someone asserted that (asserting ('my car is red' is true) is false))
>
> In the absense of negation, RDF avoids this paradox.
>
> ...
> >
> > Actually, I think that trust in metadata depends on people being able to
> > make statements like number 3.  This is exactly what is needed to allow
> > you to choose what assertions to trust.  For example, assume that your
> > list has a few more assertions:
> >
> > 8. Statement 3 is an assertion made by R
> > 9. Statement 6 is true
> > 10. Statement 7 is false
> > 11. Statement 8 is true
> > 12. Statement 9 is made by your tamper-proof digital signature checker
> > 13. Statement 10 is made by your tamper-proof digital signature checker
> > 14. Statement 11 is made by your tamper-proof digital signature checker
> >
> > Now, if you can determine that R is someone you routinely trust, you can
> > discard assertion #1, and store some internal information about person P
> > so that you know to be suspicious of him in the future.
>
> ... this is all sensible, but outside of RDF, i.e. RDF does not itself
> address the issues of 'belief' and 'trust'
>
> Jonathan
>
>
>
>
Received on Tuesday, 9 July 2002 04:03:46 GMT

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