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Re: Properties of Resources that Need More than One URI to be Identified

From: Graham Klyne <GK@ninebynine.org>
Date: Tue, 11 Nov 2003 10:57:27 +0000
Message-Id: <>
To: "James Cerra" <jimbobbs@hotmail.com>, www-rdf-logic@w3.org

I'm going to ignore the vagaries of the file: scheme, and try and respond 
more directly.

1.  If the only way you know of identifying a resource is by the 
conjunction of two related values, then RDF has perfectly respectable way 
to do this:

(Using Notation3):

   _:f a :File ;
       :localName <file:///path/name> ;
       :hostLocation :some_URI_used_to_represent_a_host_location .

This is the sort of approach that I understand underlies Guha's "reference 
by description" work [1].

2.  The fact that the only way *you* may have of identifying a resource is 
by using two values doesn't mean that it's not possible to mint a new URI 
for every resource thus described.  Here's how I do it:  given any two 
URIs, u1 and u2, I construct a new URI:


where 'uuu1' and 'uuu2' are the uris u1 and u2 with some escaping applied 
as needed to make the whole URI valid and unique with respect to u1 and u2.

I don't claim this is useful, just possible.


[1] http://tap.stanford.edu/tap/rbd.html

At 17:57 10/11/03 -0500, James Cerra wrote:

>One basic premise of RDF is that any non-anonymous resource can be 
>identified by a URI.  But what if that wasn't true?  What if there was a 
>resource that needed _two URIs_ for it to be identified?  In this case, 
>each URI, in the context of itself, could describe something completely 
>different from the thing identified by both URIs!  What would be the 
>properties of such a resource?
>For instance, say I wish to identify a file on my computer on another 
>(internet and network disabled) computer.  Note that I don't care about 
>getting the representation for that file, just identifing it.  I can't 
>just use the file: protocol since that is useful only in the context of a 
>specific machine.  However, I could use the file: scheme if I also used an 
>address: scheme (that latter specifies the location on the Earth of the 
>computer) in context.  Order is important, the address: URI wouldn't make 
>sense in the context of the file: uri.
>Unfortunately, RDF doesn't seem to handle reosurces that need multiple 
>URIs for identification.  This is troubling to me, since I have come 
>across other situations where I need more than one (or two!) URIs for a 
>concrete identification.  It would be nice; however, if there was a way to 
>combine several URIs into one identification string.
>Any suggestions or help?
>-- Jimmy Cerra
>MSN Shopping upgraded for the holidays!  Snappier product search... 

Graham Klyne
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Received on Tuesday, 11 November 2003 08:04:50 UTC

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