W3C home > Mailing lists > Public > semantic-web@w3.org > July 2009

Re: Dons flame resistant (3 hours) interface about Linked Data URIs

From: Richard Light <richard@light.demon.co.uk>
Date: Fri, 10 Jul 2009 11:35:40 +0100
Message-ID: <vsYD77N8lxVKFwN+@light.demon.co.uk>
To: Toby Inkster <tai@g5n.co.uk>
Cc: Hugh Glaser <hg@ecs.soton.ac.uk>, "semantic-web@w3c.org" <semantic-web@w3c.org>, "public-lod@w3.org" <public-lod@w3.org>
In message <1247219612.18243.10.camel@ophelia2.g5n.co.uk>, Toby Inkster 
<tai@g5n.co.uk> writes
>
>If I use the URL of my machine readable data to identity myself (myself
>being the subject of discourse) then it immediately creates ambiguities.
>
>What would it mean for the file to have a dc:created property? Would the
>value of that property be my date of birth, or would it be the date I
>first uploaded my data?

The latter, surely.  I thought there were clear conventions for 
recording metadata about/within RDF resources.

Say that you adopt the URL <http://tobyinkster.co.uk/me> as the 
identifier for the concept of you, and provide an RDF file with that 
URL.  Any RDF statements within that file with that URL as subject (or 
predicate, of course) are about you.  The file is simply a container for 
these assertions and has no identity as a subject in its own right.

>The classic example is that if I use the same URL to represent myself
>and my web page, then how can I state that I am the creator of my web
>page without also asserting that I'm my own father.

But that's my point: you shouldn't be using the same URL to represent 
yourself and your web page!  Your web page is a resource, about which 
you can make RDF assertions, including (a) that it's a human-readable 
version of the RDF associated with <http://tobyinkster.co.uk/me>, and 
(b) that the entity represented by <http://tobyinkster.co.uk/me> 
authored that page.

>The URL of the file and the URL of the subject of discourse must differ
>so that we can make unambiguous statements about each, and make
>statements about the relationship between the two.

Exactly.

>An incredibly easy
>way to do this is to just add a fragment to the URL of the subject of
>discourse. Examples include:
>
>       <http://tobyinkster.co.uk/> represents my web page
>       <http://tobyinkster.co.uk/#i> represents me
>
>       <http://id.loc.gov/authorities/sh85082139> is a web page
>       <http://id.loc.gov/authorities/sh85082139#concept> is the
>          abstract concept of Mathematics.

Yes, this also achieves the original goal, but at the expense of 
complicating life for Linked Data agents.

The page for Mathematics which you cite doesn't actually have an id 
"concept", so strictly speaking the concept URI isn't dereferenceable. 
What the agent does get is the complete page as XHTML.  It then needs to 
parse that page (N.B.), find the alternate representation:

<link rel="alternate" type="application/rdf+xml" 
href="/authorities/sh85082139.rdf" />

and go to fetch that RDF resource.  This, to my mind, reverses the order 
of priority I outlined, privileging the human-readable version of the 
subject description over the machine-processible version.  It also 
assumes that all web page authors will be as punctilious as the Library 
of Congress, in producing web pages which are XHTML and which include 
"alternate" links to the RDF.  So that's raising the bar for authors in 
a different way.

Richard
-- 
Richard Light
Received on Friday, 10 July 2009 10:36:20 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 21:45:30 GMT