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Re: [URGENT] Re: RDFa Core 1.1 XML+RDFa spec bug?

From: Nathan <nathan@webr3.org>
Date: Fri, 25 Mar 2011 09:46:57 +0000
Message-ID: <4D8C6491.9080009@webr3.org>
To: Manu Sporny <msporny@digitalbazaar.com>
CC: RDFa WG <public-rdfa-wg@w3.org>
Manu Sporny wrote:
> On 03/24/2011 10:39 AM, Shane McCarron wrote:
>> I disagree - we say this EXPLICITLY already.  For all contexts. 
>> ...
>> Note that the parent subject is set to the base value.  What am I
>> missing here?
> 
> That 'parent subject' has nothing to do with setting the 'new subject'
> when operating on the root element of the document. However, the 'new
> subject' is eventually initialized to the 'parent subject' when step #13
> is hit when processing all elements nested under the root element.
> 
> We have a problem - and I've verified that problem with Shane, Mark, and
> Gregg. This is a non-editorial problem, and is a bug with RDFa 1.0. We
> didn't see the issue until now because the XHTML+RDFa spec masked the
> problem by setting about="" on HEAD and BODY.
> 
> However, XML+RDFa 1.1 doesn't do this, but the processing rules will
> eventually set the 'new subject' to the value of 'base' via this rule in
> step #13:
> 
> http://www.w3.org/2010/02/rdfa/sources/rdfa-core/#PS-recurse
> 
> Specifically, this is run for the root element:
> 
> """
> * the base is set to the URI of the document (or another value
>   specified in a language specific manner such as the HTML base
>   element);
> * the parent subject is set to the base value;
> """
> 
> and then this
> 
> """
> the parent object is set to value of current object resource, if
> non-null, or the value of new subject, if non-null, or the value of the
> parent subject of the current evaluation context;
> """
> 
> then this is run for the element under the root element:
> 
> """
> new subject is set to the URI obtained from the first match from the
> following rules:
> ...
> otherwise, if parent object is present, new subject is set to the value
> of parent object. Additionally, if @property is not present then the
> skip element flag is set to 'true';
> """

base value = null (initial evaluation context)
parent subject = base value (initial evaluation context) = null
parent object = null (initial evaluation context)
current object resource = null (step 1)
new subject = parent object (step 6/7) = null

step 13:

the parent subject is set to the value of new subject, if non-null, or 
the value of the parent subject of the current evaluation context;
= null

the parent object is set to value of current object resource, if 
non-null, or the value of new subject, if non-null, or the value of the 
parent subject of the current evaluation context;
= null

all the values are set to null.

> That makes the resolution we made today absolutely wrong:
> 
> http://www.w3.org/2010/02/rdfa/meetings/2011-03-24#resolution_2

how?

> It also means that we have had a bug for SVGTiny1.2+RDFa 1.0 for quite
> some time (but it really didn't affect anybody).
> 
> We need to fix this before 2nd Last Call because it could result in a
> 3rd Last Call. We /could/ go into 2nd Last Call and say that we're not
> going to address this issue, but it will inevitably lead to someone
> asking why this:
> 
> <svg property="dc:title" content="The Image">...</svg>
> 
> doesn't result in a triple, but this does:
> 
> <svg><g property="dc:title" content="The Image">...</g></svg>

doesn't look like it to me! I can't say any way for that to produce a 
triple. for it to produce a triple then one of the following would need 
to be satisfied /after/ the root element has been processed:

- base != null
- parent subject != null
- parent object != null

and they are all null.

Best,

Nathan

> and why this results in a blank-node of type "foaf:Document":
> 
> <svg typeof="foaf:Document">...</svg>
> 
> The current approach to fix this is to assume about="" on the root
> element of all RDFa documents. This works across HTML, XML, SVG and all
> other document types. We already explored initializing 'new subject' to
> 'base', and 'parent object' to 'base' - they're both problematic.
> Shane's having a think on it.
> 
> Here's what we'll try to do tomorrow:
> 
> 1. PROPOSE and RESOLVE to fix the issue above, retracting the decision
>    made today about XML+RDFa and about="" (which is clearly wrong).
> 2. PROPOSE and RESOLVE to go into 2nd Last Call with the change made
>    in #1.
> 
> We will be PROPOSE/RESOLVING via this mailing list, so it is vital that
> as many RDFa WG members respond with their "+1/-1" as possible. So, keep
> your eyes peeled for the proposals tomorrow and make sure to send in
> your +1/-1 or we'll miss our narrow window for 2nd LC.
> 
> -- manu
> 
Received on Friday, 25 March 2011 09:48:08 UTC

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