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Re: Proposal for ISSUE-11: Default prefix declarations

From: Mark Birbeck <mark.birbeck@webbackplane.com>
Date: Wed, 3 Mar 2010 18:05:55 +0000
Message-ID: <640dd5061003031005rf0394cdsc10b45eb05756483@mail.gmail.com>
To: Shane McCarron <shane@aptest.com>
Cc: Manu Sporny <msporny@digitalbazaar.com>, RDFa WG <public-rdfa-wg@w3.org>
Hi Shane,

On Mon, Mar 1, 2010 at 3:58 AM, Shane McCarron <shane@aptest.com> wrote:
> +1.  The only risk I see associated with this proposal is that people might
> assume that some prefix is pre-declared when in fact it is not (e.g., my
> favorite vocab is skiing: - that MUST be in there).

There is another risk, which is that one of the prefix mappings gets
used as a URI scheme. In the current proposal a document that used the
new scheme would find the corresponding URI misinterpreted by an RDFa
parser. This is particularly worrying because the URI might have been
added by someone who doesn't know anything about RDFa.

For example, say I publish my blog with Drupal 7; since D7 contains
some RDFa support out of the box, it wouldn't be unreasonable for your
server to crawl my server and extract the RDFa. However, let's assume
that I know nothing of the RDFa under the hood, and just want to write
my blog about antelopes. Let's say also that I have used a link to
"dc:blah" in my latest post; your crawler will now interpret that as
something in the DC namespace, because of the hard-coded prefix.

I think this is just too fragile and would prefer we don't go down this route.

However, assuming for the moment that we want to explore possible
solutions, the key thing we need is a way to turn off the default
prefix mappings. One way might be to say that if we see @profile=""
then that means don't use the default mappings. Alternatively we might
say that if /any/ profile is defined, the defaults are not used. (It's
easy enough for profile authors to add the default profile back in
again.)

Having a mechanism to switch off the defaults mainly helps the
RDFa-aware author. However, it can helps the non-RDFa aware author
indirectly; in the Drupal scenario it would be best for Drupal to
switch off the default mappings using whatever mechanism was
available, because then it means that the content users enter into the
CMS is guaranteed to be interpreted correctly, whatever new URI
schemes come along.

(Drupal 7 has the ability to turn the RDFa DOCTYPE on and off on
different pages, so in a way this is the corollary of that; at the
moment they can turn RDFa 'on', but we also need a way for them to be
able to turn default mappings 'off'.)

Regards,

Mark

--
Mark Birbeck, webBackplane

mark.birbeck@webBackplane.com

http://webBackplane.com/mark-birbeck

webBackplane is a trading name of Backplane Ltd. (company number
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Received on Wednesday, 3 March 2010 18:06:32 GMT

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