W3C home > Mailing lists > Public > public-lod@w3.org > November 2010

Re: Is 303 really necessary? (Multiple things described in a single document)

From: David Booth <david@dbooth.org>
Date: Mon, 08 Nov 2010 01:27:43 -0500
To: Ian Davis <me@iandavis.com>
Cc: "public-lod@w3.org" <public-lod@w3.org>
Message-ID: <1289197663.5492.16759.camel@dbooth-laptop>
Hi Ian,

On Fri, 2010-11-05 at 10:59 +0000, Ian Davis wrote:
> I have a question about  http://thing-described-by.org/ - how does it
> work when my description document describes multiple things? Really,
> any RDF document that references more than one resource as a subject
> or object can be considered to be providing a description of all those
> resources.

It sounds like you are getting into the distinction between what I've
been calling "core assertions" and "ancillary assertions":

In a nutshell, the "core assertions" of a URI are those that the URI
owner has authoritatively provided in its URI declaration, that all
statement authors using that URI *should* accept (or else they should
not use the URI):
Statement author responsibility 3: Use of a URI implies agreement with
the core assertions of its URI declaration.

For example, the assertions about 
<http://iandavis.com/2010/303/toucan> that you provided in
<http://iandavis.com/2010/303/toucan.rdf> are *core* assertions with
respect to http://iandavis.com/2010/303/toucan , because you own that
URI.  Thus, anyone using that URI to make RDF statements about your
toucan *should* accept your assertions.  (Otherwise they may be talking
about a different toucan!)

However, if *I* make statements using your toucan URI
<http://iandavis.com/2010/303/toucan> , my assertions are *ancillary*
assertions with respect to ("WRT") that URI: other RDF statement authors
using your toucan URI are free to use or ignore my statements, because
they are not authoritative WRT that URI.

So, even though your URI declaration at
http://iandavis.com/2010/303/toucan.rdf may make assertions about many
subjects, those assertions only act as *core* assertions for
http://iandavis.com/2010/303/toucan .  They act as *ancillary*
assertions for other URIs.

Note that the exact same assertion can be a core assertion WRT one URI,
but an ancillary assertion WRT another URI.  This is normal, because
assertions that are authoritative WRT one URI declaration may be
non-authoritative WRT another URI.

The reason for this distinction between core and ancillary assertions is
to ensure that when different people talk about
<http://iandavis.com/2010/303/toucan> we can know that they are all
talking about the *same* toucan (at least within the limits of the
ambiguity in that toucan's definition).  If different statement authors
used different URI declarations for your toucan URI then they would run
the risk of talking about *different* toucans.  (Actually, they still
run the risk of talking about different toucans, as illustrated by
graphs A and C here:
but the risk is reduced.)

I'll address your other questions separately, so that this email message
doesn't get even longer.

David Booth, Ph.D.
Cleveland Clinic (contractor)

Opinions expressed herein are those of the author and do not necessarily
reflect those of Cleveland Clinic.
Received on Monday, 8 November 2010 06:28:11 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 January 2015 15:16:10 UTC