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Re: HTML 4 Profile for RDFa

From: Sam Ruby <rubys@intertwingly.net>
Date: Sun, 24 May 2009 08:10:50 -0400
Message-ID: <4A19394A.1000409@intertwingly.net>
To: Julian Reschke <julian.reschke@gmx.de>
CC: Shane McCarron <shane@aptest.com>, Philip Taylor <pjt47@cam.ac.uk>, RDFa Community <public-rdfa@w3.org>, "public-rdf-in-xhtml-tf.w3.org" <public-rdf-in-xhtml-tf@w3.org>, HTML WG <public-html@w3.org>
Julian Reschke wrote:
> Shane McCarron wrote:
>> Julian Reschke wrote:
>>>
>>> It's clear that if RDFa is to be used with prefix declarations done 
>>> with xmlns, then mixing uppercase and lowercase declarations is not 
>>> going to work.
>>>
>>> I think restricting prefixes to be lower-case (insert proper Unicode 
>>> terminology here) would be acceptable; it's easy to live with, and 
>>> avoids introducing yet another prefix declaration mechanism.
>> I would not be opposed to adding text in the RDFa in HTML definition 
>> like "prefix names SHOULD be defined in lower-case to help ensure 
>> maximum portability among parsers, since it is common for DOM-based 
>> parsers to not preserve the case of attribute names."
>>
>> I don't see there being any need to change the definition of XML-based 
>> languages like RDFa for XHTML.  After all, in XML case is preserved.  
>> Or is ot someone's goal that documents be able to be parsed as EITHER 
>> XML or HTML?  It's not my goal.  If I define a document using an HTML 
>> family 
> 
> I know Sam wants that. But if there's a simple way to achieve this, such 
> as only using lower-case prefixes, that should be totally sufficient...

Just to be clear: the idea that all XHTML documents parse identically as 
HTML is a non-goal.  It doesn't hold for scripts and titles, and won't 
for RDFa.

Given that people will see a spec for XHTML and emulate that in 
faus-XHTML served as text/html (e.g., Drupal), I would hope that one of 
the following hold true:

1) It obviously and clearly doesn't work: either the syntaxes are wildly 
divergent, or no triples are ever produced.

2) There exists a set of best practices which, if followed, means that 
conforming examples will work in either context.  Examples: always use 
'xmlns' (even if XMLns might work in HTML), or always use lowercase 
prefixes (even if upper or mixed case prefixes may work in XHTML).

At the moment, it appears that option 1 is out of the question.  I would 
submit that option 2, while it doesn't /technically/ change the 
definition of XML-based languages like RDFa for XHTML, it does 
retroactively impose a set of best practices on such usage.

- Sam Ruby
Received on Sunday, 24 May 2009 12:11:35 UTC

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