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Re: I have a trouble with The RDF Model

From: Stefan Decker <stefan@db.stanford.edu>
Date: Sun, 26 Nov 2000 09:42:04 -0800
Message-Id: <4.3.2.7.2.20001126092421.04464978@db.stanford.edu>
To: Seth Russell <seth@robustai.net>, RDF-Logic <www-rdf-logic@w3.org>
Hi,

a triple is unique - nobody can distinguish
between the triples [Bush, wonThe, Election]
and [Bush, wonThe, Election] per se.

However, as you have already observed, the source of
the triple might be relevant for believing a fact or not believing a fact.
A model theory (assigning true or false) therefore
has to include the source of the triple.
That means it should act on syntactic constructs like
([Bush, wonThe, Election] at RobustAI)
and
([Bush, wonThe, Election] at Electoral College).
These constructs are different even if the triples are identical.

This violates neither the uniqueness of triples nor
the Law of the Excluded Middle.
One could vote to include the source of the triple into the RDF datamodel
itself.
Former discussion of this question in the rdf-interest group resulted in the
expressed opinion to use reification for this purpose
(see http://www-db.stanford.edu/~stefan/updates.html ).

All the best,

         Stefan

At 07:02 AM 11/26/2000 -0800, Seth Russell wrote:
>The  RDF Model states that there is a set of resources, a
>set of properties, and a set of triples.  This seems to
>imply that in ~The Model~ triples are unique.  Take for
>example the triple [Bush, wonThe, Election] - the model
>states that there is only one such triple.  Now the fact of
>the matter is: I can see that  triple here (say at
>robustai.net) and i can see that triple there (say at the
>Electoral College).  Were I to view that triple here I would
>evaluate it to [False], were I to view that triple there, I
>would evaluate it to [True].  But bear in mind, M&S says
>there is only the one triple, and that triple can not be
>both True and False according to the Law of The Excluded
>Middle.  I think this could be a real paradox were we not to
>fix it.  I can see three possible solutions:
>
>1) The sets discussed in [The RDF Model] are really
>multisets and triples are not unique.  Therefore the triple
>I see at robust.ai is not the same triple I see at the
>Electoral College; the one can be true and the other false.
>A triple is unique only within a semantic island and we need
>to be able to express in RDF to which island it belongs.
>
>2) We go down the slippery slope where every agent must view
>triples as reified statements.  When it reads a triple it
>sees a reification quad - when it writes a triple it writes
>a reification quad.
>
>3) We toss the law of the Excluded Middle.
>
>Can we discuss ?
>
>[The RDF Model] http://www.w3.org/TR/REC-rdf-syntax/#model
>[Triples Are Not Unique]
>http://lists.w3.org/Archives/Public/www-rdf-interest/2000Nov/0233.html
>
>[Multi Valued Logics]
>http://www.earlham.edu/~peters/courses/logsys/nonstbib.htm#many-valued
>
>Seth Russell
Received on Sunday, 26 November 2000 12:49:09 GMT

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