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Re: Testing Google's Rich Snippets RDFa support

From: Philip Taylor <pjt47@cam.ac.uk>
Date: Wed, 16 Sep 2009 18:19:44 +0100
Message-ID: <4AB11E30.7020104@cam.ac.uk>
To: Toby Inkster <tai@g5n.co.uk>
CC: Othar Hansson <othar@othar.com>, RDFa mailing list <public-rdf-in-xhtml-tf@w3.org>
Toby Inkster wrote:
> On Tue, 2009-09-15 at 17:09 +0100, Philip Taylor wrote:
>> Othar wrote:
>>
>>> We surely have errors in our parsing (thanks for finding several:
>>> we'll look into these on Monday).  But we will also deviate from the
>>> standard in some cases to be forgiving of webmaster errors.  For
>>> example, we expect that some webmasters will forget the xmlns
>>> attribute entirely.
>> "we will [...] deviate from the standard" makes me believe that the 
>> above problems are an unavoidable consequence of Google's intentions, 
>> rather than just unintentional transient fixable bugs, and therefore are 
>> a serious concern (which is why I'm writing about it like this rather 
>> than just listing bugs).
> 
> I think it's reasonable to build in a degree of laxity into an RDFa
> parser. Postel's Law applies.

The RDFa specification (and also the HTML+RDFa draft, which is probably 
relevant here) defines conformance requirements for processing any 
document, valid or invalid. (Hence the discussions like 
http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2009Sep/0089.html 
about precisely how processing of certain invalid inputs should be 
specified.)

Given those requirements, implementers have no room to apply Postel's 
Law without violating the specification.

(The writers of the specification could apply Postel's Law in 
determining what requirements to specify, but that's a separate issue.)

Are you suggesting that Google should intentionally violate the RDFa 
specification? Or are you suggesting the RDFa specification should be 
relaxed to allow implementers freedom in handling invalid documents? I 
think it must be one or the other, as long as Google is claiming to 
implement RDFa.

-- 
Philip Taylor
pjt47@cam.ac.uk
Received on Wednesday, 16 September 2009 17:20:30 GMT

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