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Re: ISSUE-3 PROPOSAL: Infoset coercion

From: Ivan Herman <ivan@w3.org>
Date: Thu, 8 Jul 2010 15:43:26 +0200
Cc: RDFa WG <public-rdfa-wg@w3.org>
Message-Id: <6EF89B07-BF39-405A-B466-D54247782FA7@w3.org>
To: Manu Sporny <msporny@digitalbazaar.com>
"Confusing" is an understatement:-)

On Jul 8, 2010, at 14:56 , Manu Sporny wrote:

> On 07/08/2010 07:12 AM, Ivan Herman wrote:
>> I would like to understand what this means in practice.
>> What you seem to describe is that if
>> 1. I use xmlns:XXX in HTML5+RDFa (which is probably a bad idea anyway:-)
>> 2. I have an XML processor that is namespace aware, then this is what I get
>> But what do we say if an XML processor is _not_ namespace aware?
> The concern isn't with XML Processors, since all the major ones are
> Infoset-based and are thus namespace aware. All the ones used by the
> browser manufacturers fit this model anyway - they're all Infoset-based
> processors.

Ok, I understand (I think). But the text you refer to says:

If the XML API is namespace-aware, the tool must [...] when converting the non-XML mode DOM into an Infoset. Given a standard xmlns: definition[...]

So what you say is that all XML API is namespace aware, that we do not have to deal with non-namespace aware API-s. Is that correct? (I used the term XML processor, my mistake, this is probably the same as XML API, right?)

> The concern is with non-XML processors, such as SGML-based processors,
> which is the category that HTML5 non-XML mode falls into. Non-XML mode
> processors are not namespace aware.

So where SGML-based processors come into the picture exactly? In browsers when parsing HTML5? Apologies for my ignorance...

> There is concern in WHAT WG and HTML WG that nobody defined the
> algorithm for translating an SGML-based document model into an
> Infoset-based document model.
> In other words, in HTML5 (non-XML mode), nobody says how to generate a
> namespace tuple... to get from this (in a non-XML HTML5 document):
>   xmlns:foo="http://example.org/foo#"
> to this (in the Infoset):
>   [http://www.w3.org/2000/xmlns/, foo, http://example.org/foo#]
> Some people in HTML WG and WHAT WG are arguing that non-XML mode models
> shouldn't be namespace aware at all because SGML isn't namespace aware.
> Namespaces are a DOM2 and Infoset thing. The counter-argument to that is
> that RDFa needs the namespace information - we depend on it for xmlns:
> to work correctly, and thus don't have the luxury of ignoring namespace
> information.
> There is also a parallel issue - we'd like the HTML5 non-XML mode model
> and the XHTML5 (XML-mode) model to be equivalent. By having namespaces
> in one and not the other, the two models are not equivalent. Since the
> two models are, currently, not equivalent - the HTML WG and WHAT WG
> folks are saying that the triples generated from a document /could/
> potentially be different between HTML5 and XHTML5 mode. That would be a
> bad thing.
> To remedy this, we are trying to create language that makes it clear how
> namespace information is extracted from an HTML5 non-XML mode document
> as well as an XHTML5 XML-mode document.
> We don't /need/ to modify the coercion to Infoset rules in the HTML5
> spec for this to work. However, modifying the coercion to Infoset rules
> is the correct technical solution.
> If HTML WG rejects the coercion to Infoset rule changes, we can always
> fall back to defining how one extracts the namespace information from a
> HTML5 non-XML mode document (for Infosets and for DOM Level 2).

But... is this something that should go into the HTML WG?

What I mean is: what will a non-XML SGML parser do with xmlns:foo="bar"? I would expect that it would use an attribute with name "xmlns:foo" with value "bar". So the RDFa specification may very well define a mapping from this to our prefixes and CURIES, completely bypassing the notion of a namespace. That is in case the HTML5 WG does not want to accommodate...

On the other hand... we already deprecate, in so many words, the usage of xmlns: for HTML5. So, in RDFa1.1 and SGML and non-XML and stuff we can just say: use @prefix... (I know, this is not 100% kosher, but just puts things in perspective...)


> I know this is confusing - hopefully I'll be able to do a better job
> explaining this on the call today.
> -- manu
> -- 
> Manu Sporny (skype: msporny, twitter: manusporny)
> President/CEO - Digital Bazaar, Inc.
> blog: Myth Busting Web Stacks - PHP is Faster Than You Think
> http://blog.digitalbazaar.com/2010/06/12/myth-busting-php/2/

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
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Received on Thursday, 8 July 2010 13:43:47 UTC

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