Re: Request to publish HTML+RDFa (draft 3) as FPWD

On Sep 18, 2009, at 18:40, Manu Sporny wrote:

> Henri Sivonen wrote:
>> Section 2 is marked as normative although its content is devoid of
>> normative statements.
> Your most recent issues have been added to the HTML+RDFa issues list:


>> I observe that four out of the six deferred issues depend on the two
>> issues you left open. (I disagree with the characterization of the
>> deferred issues as "implementation details".)
> I'd like to setup a time that we could discuss this over the phone  
> as I
> want to make sure that I understand the issues that you see moving
> forward.

I'll follow up on this off-list.

> You've raised the XOM issue multiple times and we have yet to
> see a XOM implementation of RDFa, so it is a valid concern.
> In general, we could say that a parser, model or other view of the
> document that doesn't allow one to retrieve namespace declarations is
> not capable of implementing RDFa. If XOM falls under this class of
> parsers, then it is not capable of implementing RDFa.

(XOM is a tree model--not a parser.)

Indeed, declaring a Willful Incompatibility with tree models that  
properly reflect the XML Information Set would be one way to approach  

Trying to restate my concern:

Here are four propositions about RDFa that can be true or false:

1) The syntax xmlns:p="" defines a prefix mapping  
from 'p' to ''.

2) The prefix mapping from 'p' to '' is represented  
in the same way in the tree model regardless of whether the tree model  
was built by an HTML parser or by an XML parser.

3) An implementation of the HTML parsing algorithm (as defined in  
HTML5 as of 2009-09-21) can be used to build the tree model without  
modifications to the algorithm and without a tree rewriting step  
(other than optionally the Coercion to Infoset rules from HTML5)  
between the parser output and the RDFa processor input.

4) A tree model that completely, correctly and exclusively reflects  
the XML Information Set can be used as the tree model.

(For clarity: DOM Level 1 isn't a tree model that completely,  
correctly and exclusively reflects the XML Information Set.)

I want #2, #3 and #4 to be true, although I'd prefer not to have  
prefix mapping mechanism at all. Presumably, you want #1 to be true.  
More generally, I dare speculate that for each of these propositions,  
you can find people (apart from just you and me) within the HTML, RDFa  
and XML communities who want the proposition to hold true.

The problem is that all the four propositions cannot be true at the  
same time. At least one of them has to be false.

What I'm asking is that instead of leaving this inconvenient situation  
for RDFa implementors to discover as an "implementation detail" when  
they've already committed to a tree model and a parser, you make the  
choice of which one of the propositions you choose to make false and  
be very explicit about this choice in the spec. (Or, alternatively, if  
you wish to offer implementors a choice of which one to make false,  
I'm asking you to make the need for the implementor to make the choice  
very explicit in the spec.)

Henri Sivonen

Received on Monday, 21 September 2009 07:39:16 UTC