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Re: the meaning of RDF tokens

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 17 Feb 2003 06:26:58 -0500 (EST)
Message-Id: <20030217.062658.07060718.pfps@research.bell-labs.com>
To: fmanola@mitre.org
Cc: www-rdf-comments@w3.org

From: Frank Manola <fmanola@mitre.org>
Subject: Re: the meaning of RDF tokens
Date: Thu, 13 Feb 2003 14:08:22 -0500

> Peter--
> 
> Thanks for this comment.  I believe this is roughly the same point you
> made in your review of the pre-last-call documents of 26 December 2002,
> where you said
> 
> > The Primer starts the unfortunate blurring between RDF, a simple formalism,
> > and the entirely of human understanding in its talk about knowing the
> > ``exactly what is meant by'' http://purl.org/dc/elements/1.1/creator.  It
> > would be much better to avoid anything in the Primer that even hints that
> > an  RDF processor will be able (or, worse, required) to understand exactly
> > what is meant by such things, as their meaning includes a gigantic portion
> > that is outside of RDF.
> 
> Can you confirm that?  

Yes, basically.  

> In my response to your original comment, I had
> said:
> 
> > When I referred to a program "that understands 
> > http://purl.org/dc/elements/1.1/creator" I was thinking in terms of a 
> > program *written* to understand that particular term (or written to 
> > behave according to that term's definition when it encountered it) 
> > rather than a generic RDF processor that somehow sucked in that 
> > "understanding".  But I see how the problem you mention can arise.  I'll 
> > try to make that clearer (I think it's still necessary to mention 
> > "programs", but I agree that the limitations of what "understanding" RDF 
> > provides to those programs needs to be clarified).
> 
> Do you believe that this sort of clarification will address the issue
> you raise? 

To some extent.  The problem is not only in the part of Section 2.2 that
I mentioned, but is also sprinkled throughout the RDF documents.  The
notion of social meaning as a normative part of RDF means that the entire
RDF specification has to be extraordinarily careful about conflating formal
and informal meaning.

> I generally understand your concern as being to clearly
> separate the meaning that RDF itself specifies from any additional
> meaning that has to be read into such tokens by humans (and programs
> they write based on that additional meaning).  Is that correct?  I'll
> run the actual proposed rewrite by you if you like (as soon as I come up
> with it).

Agreed.  The issue is that there are several senses of ``meaning'', as the
response by Pat pointed out.  Again, because the RDF documents elevate this extra
(informal, social, ...) meaning to a normative part of the RDF
specification, all the RDF documents have to be extraordinarily careful to
maintain a clear separation between the various senses of ``meaning''.

> In accordance with the change recording process we're using, I had
> assigned your original comment a change id of #primerLCC-010.  If you
> feel that this new comment is distinct from that one, could you please
> clarify the difference (and I'll add an additional change)?  Thanks
> again.

Only one last-call comment identifier is needed here, I think.  However, I
do not see any in the last-call comment list at
	http://www.w3.org/2001/sw/RDFCore/20030123-issues

> --Frank

peter



> "Peter F. Patel-Schneider" wrote:
> > 
> > The RDF primer, in Section 2.2, states
> > 
> >         Using URIrefs as subjects, predicates, and objects in RDF
> >         statements allows us to begin to develop and use a shared
> >         vocabulary on the Web, reflecting (and creating) a shared
> >         understanding of the concepts we talk about. For example, in
> >         the triple
> >                 ex:index.html  dc:creator  exstaff:85740 .
> >         the predicate dc:creator, when fully expanded as a URIref, is an
> >         unambiguous reference to the "creator" attribute in the Dublin Core
> >         metadata attribute set (discussed further in Section 6.1, a
> >         widely-used set of attributes (properties) for describing
> >         information of all kinds. The writer of this triple is effectively
> >         saying that the relationship between the Web page (identified by
> >         http://www.example.org/index.html) and the creator of the page (a
> >         distinct person, identified by
> >         http://www.example.org/staffid/85740) is exactly the concept
> >         identified by http://purl.org/dc/elements/1.1/creator. Moreover,
> >         anyone else, or any program, that understands
> >         http://purl.org/dc/elements/1.1/creator will know exactly what is
> >         meant by this relationship.
> > 
> > This appears to me to state that the meaning of tokens in RDF *is*
> > their commonly agreed on meaning, regardless of how that meaning is
> > specified.  If so, this means that RDF reasoners are responsible for
> > implementing this meaning.
> > 
> > Is this actually the case?  If so, how can RDF reasoners be implemented?
> > If not, please explain what the above quote means.
> 
> -- 
> Frank Manola                   The MITRE Corporation
> 202 Burlington Road, MS A345   Bedford, MA 01730-1420
> mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-8752
Received on Monday, 17 February 2003 06:27:10 GMT

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