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RE: SemWeb Non-Starter -- Distributed URI Discovery

From: Miles, AJ \(Alistair\) <A.J.Miles@rl.ac.uk>
Date: Fri, 1 Apr 2005 15:10:29 +0100
Message-ID: <F5839D944C66C049BDB45F4C1E3DF89D18DC4A@exchange31.fed.cclrc.ac.uk>
To: "Stephen Rhoads" <rhoadsnyc@mac.com>, <semantic-web@w3.org>, <www-rdf-interest@w3.org>

> As far as I can tell, there is no formal, generalized 
> mechanism to reliably query the owner of a URI in order to 
> obtain an RDF Description of that URI.  And this is a serious 
> impediment to the Semantic Web.

I think this hits the nail on the head.  

A couple of thoughts ...

First this extends beyond HTTP - how might one implement this for URN for example?  Considering HTTP URIs only, URIQA is the only thing I know of that actually satisfies this requirement fully, but it would take a lot of time and effort to migrate to an http web that supports URIQA.  Any other ideas?

Second, there is a more general discovery requirement which can be loosely phrased as, 'I want to find out what x said about y,' or, 'who said what about what?'  I have no ideas for how to solve that.

Finally, scoping this problem to just http uris used to denote non-information resources, my currently favoured position is that all such resources (whether denoted by hash or slash URIs) should support the SPARQL protocol (when it's done :)

Cheers,

Al.

 


> 
> "hashing" at least gets you part of the way because -- given 
> an HTTP URI containing a hash and frag ID -- it is *likely* 
> that one can dereference the URI into a document containing 
> (amongst other things) an RDF description of the URI in question.
> 
> For example, if I encounter the URI
> 
> http://www.somemediacompany.com/rdfdata/music/classical#resource
> 
> chances are I can dereference 
"http://www.somemediacompany.com/rdfdata/music/classical" and find within that document an RDF description of "#resource".

If, one the other hand, I encounter

http://www.somemediacompany.com/rdfdata/music/classical/resource

then I can't make any assumptions about whether or not this URI refers to some sort of document containing an RDF description of "resource".  The URI owner may just have chosen to mint URIs using some logical hierarchy.

So, given an arbitrary URI, how can I obtain an RDF Description of that URI?

I suppose I could crawl the domain "containing" the URI with a spider and harvest RDF data until I find the description I'm looking for, but that's a bit of a mess.  And it certainly doesn't scale.

I read up a bit on SPARQL -- particularly the "SPARQL Protocol for RDF" -- and, unless I'm misunderstanding, it seems to be the intended long term solution to the problem described herein.  Is that correct?  Is it expected that URI owner/minters will operate some sort of SPARQL server for providing RDF Descriptions of their URIs?  Will there be some convention as to the location of these servers such that one can *reliably* and automatically query for an RDF Description of a URI?

Have I framed this problem correctly?  Are there solutions or angles which I have missed?  Input would be greatly appreciated.

--- Stephen

[1] http://www.dmmp.org (Digital Media Metadata Project)
Received on Friday, 1 April 2005 14:15:51 GMT

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