W3C home > Mailing lists > Public > semantic-web@w3.org > April 2008

Re: Person Identifier

From: Andreas Langegger <al@jku.at>
Date: Mon, 21 Apr 2008 12:45:17 +0200
To: "Mark Birbeck" <mark.birbeck@x-port.net>
Message-Id: <2817E761-4F9B-45DB-A428-06C44034AAA6@jku.at>
Cc: "Richard Cyganiak" <richard@cyganiak.de>, "Bent Rasmussen" <incredibleshrinkingsphere@gmail.com>, semantic-web@w3.org

On Apr 21, 2008, at 12:16 PM, Mark Birbeck wrote:
> That depends on what you think 'the problem' is. :) In RDF, I can
> write triples down on the back of an envelope. Any statements I make
> are in some sense true (at least in the world I have created that is
> described by my envelope), regardless of the presence of a network.

Maybe the question is, how much should a mere identifier reveal about  
the thing it actually represents?
Should it include any information at all? URIs don't change, but such  
meta data could. Well, an entity's type won't change, so the type  
could be part of the global ID: in URN's it's a prefix, in HTTP URIs  
it could be "somewhere" in the URI (e.g. as sub domain).

> To put it a different way, RDF is a way of making statements about
> anything you like. Obviously, some of the things we want to make
> statements about are web-pages, but most of them are not. So the
> argument being pursued (and I know it's not just your position, but
> one that is widely held) is that we need to establish a connection to
> the internet before we can deduce that some person is *not* a
> web-page.

> GET requests may be simple, but how can making one be easier than
> *not* making one?

What if we find a way to "optionally" make one to find out more about  
the resource and include the type in the URI? If not included, the  
client will have to do a GET, otherwise it may chose freely to fetch  
more triples.

> URIs are transparent to RDF. They are simply identifiers. You can hack
sure, but URNs too.

> them up all you like, but you can't expect RDF to start unpacking the
> hacks.  The problem with URIs comes when using one identifier to

That's right. The same applies if you use URNs for RDF resources.  
Applications will have to "unpack" the hack (or do I miss sth?)

> represent two different things. That's a problem whichever way you
> look at it, whatever the two things are, not just web-pages and
> people.

First I also disliked the idea that HTTP URIs should represent non- 
informational resources. The fact, that an URI is usually representing  
a web page is so deeply anchored in our thinking that it just sounds  
too obscure.

I think the remaining argument against URIs everywhere + HTTP only is  
that you may have to do thousands of GET requests for a large KB,  
especially when you need that information NOW to reason over it - but  
that's not solved with URNs. The additional non-HTTP schema prefix or  
hyphen is poor information also and you may want to know more anyway  
and fetch information from the web first.


> Regards,
> Mark
> -- 
> Mark Birbeck
> mark.birbeck@x-port.net | +44 (0) 20 7689 9232
> http://www.x-port.net | http://internet-apps.blogspot.com
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Dipl.-Ing.(FH) Andreas Langegger
Institute for Applied Knowledge Processing
Johannes Kepler University Linz
A-4040 Linz, Altenberger Straße 69
Received on Monday, 21 April 2008 10:46:16 UTC

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