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Re: Some further thoughts on the default profile issue ( ISSUE-78 and ISSUE-73 )

From: Ivan Herman <ivan@w3.org>
Date: Mon, 31 Jan 2011 16:23:02 +0100
Cc: W3C RDFa WG <public-rdfa-wg@w3.org>
Message-Id: <17FAA3E0-D099-476E-8101-E0F71AB63868@w3.org>
To: Toby Inkster <tai@g5n.co.uk>
I have only one comment: ouch:-)


On Jan 31, 2011, at 16:04 , Toby Inkster wrote:

> On Mon, 2011-01-31 at 10:44 +0100, Ivan Herman wrote:
>> However, from a spec writing and definition point of view, it may also
>> simplify one thing. The current rule is that if we have a CURIE, but
>> the prefix does not resolve to a defined URI, then the whole CURIE is
>> considered to be a full URI. This is how we could accommodate having
>> @rel="http://www.example.org/bla". But... we could also remove this
>> thing altogether (thereby making things simpler and closer to RDFa
>> 1.0. Instead, we could agree that the default profile would include
>> the prefix mapping 'http' -> 'http:' (and the same for a bunch of
>> other http schemes).
> That would work for "http:", but not for, say, "urn:". Why? 
> Take for example the mapping "urn"=>"urn:". We want to then represent
> the IRI <urn:isbn:0123456789> as a CURIE.
> The suffix part of a CURIE is defined as an irelative-ref (from the IRI
> spec). This in turn is defined as an irelative-part optionally followed
> by a query string and fragment. Focusing on the irelative-part, it can
> be one of:
> 	1. something that has an authority
>           (which will always start "//", so not relevant here)
> 	2. an absolute path
> 	   (which will always start "/", so ditto)
> 	3. an ipath-noscheme
> 	4. empty
> OK, so clearly if we're representing that ISBN IRI as a CURIE, we're
> needing to use ipath-noscheme, but drilling down into the definition of
> that, an ipath-noscheme cannot contain any colons before its first slash
> (it's not required to contain a slash though).
> So the mapping "urn"=>"urn:" cannot be used to create a CURIE for
> <urn:isbn:0123456789>. (Which is not to say that this IRI can't be
> represented as a CURIE - it can - you just need to create a different
> mapping, such as "urn-isbn"=>"urn:isbn:".)
> A possible fix would be to broaden the allowed syntax for CURIEs. The
> suffix part of a CURIE (a.k.a. reference) would be defined as any string
> containing no whitespace characters. (And we do already define
> whitespace.) It would not surprise me if we discovered that many RDFa
> implementations already use that definition.
> [ Aside: the current definition of CURIE needs fixing anyway. The empty
> string (i.e. no prefix, no colon and no suffix) is allowed as a CURIE,
> which will map to the "no prefix" mapping with nothing appended.
> However, it's impossible to detect an empty string CURIE in a
> whitespace-delimited list; and we do not interpret datatype="" as being
> the empty string CURIE. We should almost certainly explicitly forbid the
> use of the empty string as a CURIE. (Though we should still allow it as
> a safe CURIE.) ]
> In general I'm in favour of this suggestion, but I do think it needs to
> be combined with this broader syntax definition for CURIEs.
> We'd need to discuss which URI schemes get included in the default
> profile.
> -- 
> Toby A Inkster
> <mailto:mail@tobyinkster.co.uk>
> <http://tobyinkster.co.uk>

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Monday, 31 January 2011 15:22:51 UTC

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