W3C home > Mailing lists > Public > public-rdf-in-xhtml-tf@w3.org > July 2008

Re: RDFa test suite addition

From: Mark Birbeck <mark.birbeck@webbackplane.com>
Date: Wed, 30 Jul 2008 07:46:39 -0400
Message-ID: <ed77aa9f0807300446p2043f83dk49aea034b159402@mail.gmail.com>
To: "Hausenblas, Michael" <michael.hausenblas@joanneum.at>
Cc: "Manu Sporny" <msporny@digitalbazaar.com>, "RDFa mailing list" <public-rdf-in-xhtml-tf@w3.org>

Hi Michael,

> I do by and large agree with Mark (i.e. his excellent description,
> below) BUT in the same moment I'd like to point out the 'Opacity Axiom'
> [1], [2].

I'm afraid I don't follow you. I'm not sure what you mean when you say
that you agree with me BUT want to draw attention to the question of
opacity, since I don't know which part of what I am saying detracts
from opacity.

Having said that, I'd also say that I don't see opacity of URIs as
relevant to this discussion. :)

> Please note as well that in RDF we talk about URIrefs [3] and
> *relative URIs are not used in an RDF graph*

That's right. As I said before, I made sure to make that point in the
spec, and also pointed to the algorithm that should be used to turn
relative paths into absolute ones. Following that algorithm for all
URIs when parsing will remove *all* of the issues we have been

> - FWIW, I'm happy to take
> an action to evaluate how other RDF serialisations (e.g. RDF/XML, or
> upcoming such as Turtle [4]) are dealing with this situation.

I doubt anyone will stop you. :) But I'm not sure you'll find anything
surprising; absolute URIs are fundamental to RDF, so they are used
everywhere. Different serialisations allow different ways to
abbreviate those URIs, but that doesn't change that the underlying
identifier is an absolute URI.

RDF/XML supports relative paths and QNames/namespaces as abbreviation
mechanisms, whilst XHTML+RDFa supports relative paths and CURIEs as
abbreviation mechanisms.

But as far as RDF is concerned everything must be an absolute URI.

I hope we don't get too side-tracked here; I think the issue is pretty
straightforward, and the only question I think we have to answer is
whether the spec should be more explicit, or whether it already says



Mark Birbeck, webBackplane



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Received on Wednesday, 30 July 2008 11:47:17 UTC

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