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questions on assertion

From: Giles Hogben <giles.hogben@jrc.it>
Date: Mon, 1 Jul 2002 14:23:13 +0200
Message-ID: <00f301c220fa$12245900$162abf8b@pcdsa22>
To: <www-rdf-interest@w3.org>, <www-rdf-logic@w3.org>

I am confused about the meaning of assertion as used in the RDF model theory
spec and would appreciate some clarification:
Looking at the following phrase in the model spec,

"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."

I looked for a definition of what you take assertion to mean and I couldn't
find anything in the w3 RDF site which fitted in this context (or others in
which the term is used in the document) and nothing specifically within the
model document at all.
On the absence of a formal definition of how the noun "assertion" is used, I
would take to mean that the triples are asserted by the author of the rdf
store to be true, which is the standard use of the term

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
2. X is statement 1.
3. X is not true.
4. my car has four wheels
5. Y is statement 4.
6. X is an assertion made by P
7. Y is an assertion made by Q

It seems to me that there are problems with expressing these statements in
RDF,  given the assumptions regarding assertion - mainly.

1. If we interpret an assertion to mean "I believe 'my car is red' is true."
then how do we interpret 3. Surely this is saying:
If  "my car is red" in rdf carries an implicit assertive meaning, then  it
is saying:
"I believe 'my car is red' is true"
But then 3. is saying:
"I believe ["I believe 'my car is red' is true"] is false"
Which is a paradox.
So the problem I am getting at, is how can say, without creating a logical
inconsistency, that one believes a statement in rdf data is false?
This is in my view a real problem for applications involved in reputation
and trust.
2. If rdf statements implicitly carry assertion, how can I specify the
author of the assertion? That is - does the assertion implied by 1. also
imply something about who is making the assertion (is it the author of the
document?) - then how do I change that if I want to in a statement like 7.



_____________________________________________
Giles Hogben
Institute for the Protection and Security of the Citizen (IPSC)
European Commission - Euratom Centro Comune di Ricerca
Received on Monday, 1 July 2002 08:18:53 GMT

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