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Re: Again: Anonymous Resources and literals

From: Graham Klyne <GK@ninebynine.org>
Date: Mon, 12 Mar 2001 14:26:20 +0000
Message-Id: <5.0.2.1.2.20010312140140.03a37020@joy.songbird.com>
To: Jan Grant <Jan.Grant@bristol.ac.uk>
Cc: RDF interest group <www-rdf-interest@w3.org>
Jan,

At 10:53 AM 3/12/01 +0000, Jan Grant wrote:

>Have a look at http://tribble.ilrt.bris.ac.uk/~cmjg/rdf/discuss -

I started my message to disagree with this bit:

>There are obviously situations where we may need to have reference to the 
>same resource multiple times (perhaps someone who is both an author and 
>editor of a
>book appears twice in the capacity of 'contributor'). However, looking 
>more closely at this example, it is evident to me that a set would more 
>than suffice. Why?
>Well, are we solely interested in whether Joe Bloggs is a 'contributor'? 
>If so, he either is, or he isn't. Set membership works like that. Are we 
>interested, instead, in
>the number of times or the different roles that Joe Bloggs contributed? In 
>which case, surely the collection we're talking about is a set of events 
>or roles which carry
>the extra information required to distinguish 'Joe Bloggs as author' from 
>'Joe Bloggs as editor'. That's why I think bag should have been set.

...but then realized that it might shed some useful light on the way 
literals may be handled (something that you may have been alluding to later 
when you mention "virtual nodes"?), and that I would then be fully in 
agreement with the above.

My counter-example was to be the book with three authors named "Smith", 
"Smith" and "Jones".  To represent the raw information from which one could 
draw up a list of the book's authors, I think that a bag, not a set would 
be required.  But note that this argument only makes sense if the authors 
are represented by their literal names, which (in RDF terms) is a rather 
half-hearted approach to capturing the knowledge.  If the authors were 
represented by resources, then everything you say above would apply.

This led me to thinking that a literal should maybe stand for an anonymous 
resource which happens to have a property:

   [ >-rdf:value-> data:,Smith ]

By this approach, the two "Smith" literals would stand for different resources.

...

On a related note, I wonder if our discussions are not in danger of 
conflating two distinct issues:

   anonymity of resources (which I take to mean that we don't *know* their URI)
and
   existential quantification of a resource.

(I'm still undecided whether I agree that existential quantification is a 
distinguished feature of a resource or whether at some level *all* 
resources are thus quantified.  Following discussions in Boston, I do agree 
that some distinction is needed for practical purposes when performing 
queries in an RDG graph, but I'm not yet sure that "Backwards E" is it.)

#g


------------
Graham Klyne
GK@NineByNine.org
Received on Monday, 12 March 2001 09:41:41 GMT

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