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web proper names redux

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Sat, 25 Sep 2004 19:04:15 -0400 (EDT)
To: www-rdf-interest@w3.org
cc: ht@inf.ed.ac.uk
Message-ID: <Pine.LNX.4.44.0409251635460.20584-100000@tribal.metalab.unc.edu>

Thanks everyone on this list who discussed the Web Proper Names proposal. 
A number of questions have been proposed, and the discussion
went off to discuss a number of related proposals such as URIQA that have
differeing methods for solving the problem of the potential ambiguity 
between when a URI is used to represent a referent (such as me) or a 
representation of a referent (such as a webpage). As put by David 
Menendez, "As I see it, some URIs identify web pages and other identify 
abstract, non-web-page things".

For those interested, I'm going to clarify the options for those wishing 
to make the distinction (or similar ones, such as that between a resource 
itself and those representations which it may return). Then I will take
leave of what many may consider a philosophical rat-hole, and any further
communication with me on this subject should take place via e-mail since
I'm sure the www-rdf-interest has more things to discuss at this point:

1) The problem could be solved by using a new URI Scheme, such as 
the contextualized wpn:// or the less contextualized Larry Masinter
tdb:// proposal (http://larry.masinter.net/duri.html). 
2) The problem could also be solved by allowing a representation itself
to be used to denote a referent, and the Expanded Web Proper Bame 
format does that with the goal of interoperability in mind. 
http://www.cogsci.ed.ac.uk/~ht/webpropernames/
3) Jon Hanna had an RDF schema (rough draft) for distinguishing between
resources and representations:
http://www.hackcraft.net/rep/rep.xml 
4) Thomas Passim had a few RDF predicates that could help:
	 subjectIsTheThingReturnedByThisURI,  
	theDocumentAtThisUriDescribesTheSubject, 
	TheDocumentAtThisUriIsAboutTheSubject - which were not discussed
much further, although it's another route.
5) The problem could also be solved by simply grounding a URI in "a 
RDF graph where the terminal nodes are either URI references, 
literals, or anonymous nodes not serving as the subject of any 
statement", which might be even easier with a few new HTTP methods, 
as suggested by URIQA and Patrick Stickler.
( http://swdev.nokia.com/uriqa/URIQA.html)

I tend towards the human-readable representation viewpoint to solve the 
"URI-grounding" problem, although I find the URIQA model (minus the new 
http)and the RDF predicate/schema models also interesting avenues. 

There are definitely some differing views on how URI works. In the ideal
semantic web world, at Patrick Stickler put it, "URIs should not be used 
to denote more than one thing. Period. Only the creator of a URI can say 
what it denotes." Then, as pointed out, this excludes us from
making statements about documents on the Web, especially when the creator
does not say what it denotes or I wish to use a  human-readable 
representation to make clear what is being denoted. Phil Dawes suggested
"They are solved in the same way as they are solved in real life - using
context." WPNs formalize some context, and so do others, and this problem 
is notoriously hard. You could always,  as Graham Klyne points out, use a 
# at the end to make the differentiation. Jon Black notes that "When a URI 
denotes, it does so because everyone in a group knows what it denotes", 
which as he notes is difficult if not impossible in a completely open 
system such as the SW. Hamish returns to the point of representation, "To 
humans, being able to dereference a URI and find some explanation of what 
that URI qua symbol is intended toindicate is very valuable indeed, and I was starting from the assumption
that http URIs would be used, as symbols, to indicate non-web resources.", 
and David Menendez follows "there's no reason that a software
agent couldn't do the same." So clearly there's no consensus on this
issue and exactly how URIs should be used in the SW - perhaps we can only 
hope for some Best Practice guidelines from above to clarify the issue, or 
see empirically how it works in the coming months and years. 
             
Again, I would say interoperability between any type of ontology or 
metadata is going to be difficult, especially where the 
semantics are unclear, humans may not be too careful about their 
use of statements (or worse, machines making statements  
automatically!), and so on. The URIQA proposal has an algorithm for
grounding RDF in other RDF, while the WPN proposal could ground RDF
statements in human-readable representations that are easy to build
and compare. 

So one could clarify a statement given in FOAF such as:

 <foaf:image rdf:about="http://www.ibiblio.org/hhalpin/homepage/images/harrytrain.png">
          <foaf:depicts rdf:resource="http://www.ibiblio.org/hhalpin.wpn"/>
 </foaf:image>

	Where http://www.ibiblio.org/hhalpin.wpn is a google on myself
where I've verified and collected useful web-pages with info about me on 
them, collating them into a EWPN.

	 We'll revise WPN a bit when we have some working code and have 
fully digested all the comments we have received. And as pointed out by 
the "OWL and the Real World" discussion, this is difficult 
going...but rewarding, since I think these types of proposals show how
a SW might communicate and grow, and as we put it, to avoid the "real risk 
that the Semantic Web will consist of a vast number of self-consistent but 
mutually incommensurable collections of metadata."                                                                                
  
			thanks everyone,

				-harry
Received on Saturday, 25 September 2004 23:04:16 GMT

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