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Re: Small change to the relationship between head and body during parsing

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Thu, 20 Dec 2007 13:14:54 +0000
Message-ID: <a707f8300712200514i2bbc0171re67b3a2a04d90852@mail.gmail.com>
To: "Ivan Herman" <ivan@w3.org>
Cc: "W3C RDFa task force" <public-rdf-in-xhtml-tf@w3.org>

Hi Ivan,

Since this will have little impact on most documents, we can still
come back to this later if we want to. I was imagining that in the
future the @xmlns technique would be phased out. :) But since that is
only my opinion, and is a long way off, there's no point in putting
the cart before the horse...so I'll remove the modification.

Thanks for taking a look at it. (It came up because I was
cross-referencing with CURIEs, but looking at it again, it's not as
important as it seemed at first.)

Regards,

Mark

On 20/12/2007, Ivan Herman <ivan@w3.org> wrote:
> Hm. I am not sure...
>
> What would be the case with an xmlns setting in the <head> element? Your
> model would mean that those xmlns settings should be valid for the
> <body> as well. This is very counter-intuitive for anybody used to
> proper XML handling, because it would be wrong from an XML point of
> view. If, in any later version of RDFa, we decided to use xml:base, for
> example, then we would run into the same issue (I guess the same holds
> for xml:lang, and possibly other that I may forget). I think I would
> prefer to stay with the clean XML model.
>
> Yes, there are special elements in the <head> that have a 'semantic'
> effect on the rest of the document (your <base> example, for example).
> This is a consequence of the html semantics, and we may have to add
> special rules in a later release to account for that if we need to. But
> I do not find those arguments convincing enough to introduce a hidden
> DOM reorganization...
>
> B.t.w., your example:
>
> <link id="dc" rel="prefix" href="http://purl.org/dc/elements/1.1/" />
>
> is actually not solved via the DOM reorganization either, it would need
> some extra 'semantics' in RDFa anyway...
>
> Sorry Mark:-)
>
> Ivan
>
> Mark Birbeck wrote:
> > Hello everyone,
> >
> > I've made a small change in the draft to the way that processing
> > occurs in terms of the hierarchy. Ordinarily I'd propose this to the
> > group, have discussion, etc., but given we are up against it in terms
> > of time, I've put it straight into the draft in a self-contained
> > block, so that if the consensus is against what I'm suggesting, it is
> > easy to simply remove it.
> >
> > I'll explain the changes first, and then the justification. The change
> > is in a note, as follows:
> >
> > <div class="explanation">
> > Note that since the head contains information that determines how the
> > body should be parsed, the [evaluation context] as set at the end of
> > processing <code>head</code> is then passed to the processing of
> > <code>body</code>. It is <em>as if</em> instead of the DOM looking
> > like this:
> > <example>
> > document object
> >   |
> >   |__ html
> >         |
> >         |__ head
> >         |
> >         |__ body
> > </example>
> >
> > it looked like this:
> >
> > <example>
> > document object
> >   |
> >   |__ html
> >         |
> >         |__ head
> >               |
> >               |__ body
> > </example>
> > </div>
> >
> > In current documents this is unlikely to make any difference at all.
> > However, my motivation for doing this is so that any [URI mappings]
> > that are set in <head> get passed on to <body>. This allows us to
> > invent some new scheme in the future, such as:
> >
> >   <link id="dc" rel="prefix" href="http://purl.org/dc/elements/1.1/" />
> >
> > or whatever we come up with, and have the prefixes apply across the
> > document. With the current parsing model that wouldn't work.
> >
> > Note that this is important for a number of reasons:
> >
> >   * when we come to look at HTML we can do CURIEs without having to rely
> >     on @xmlns;
> >
> >   * there was a lot of opposition to using XML namespaces _anyway_;
> >
> >   * it is actually more 'logical', since the head does already set
> > information for the
> >     document that could not be determined by applying a simple
> > hierarchical processing
> >     model (for example, <base> would not apply to the entire document);
> >
> >   * the IPTC had a lot of problems with the prefix mapping question,
> > because they
> >     wanted to be able to refer to a great big block of prefix
> > mappings, sometimes in
> >     an external document, and this technique would allow that.
> >
> > Regards,
> >
> > Mark
> >
>
> --
>
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf
>
>


-- 
  Mark Birbeck, formsPlayer

  mark.birbeck@formsPlayer.com | +44 (0) 20 7689 9232
  http://www.formsPlayer.com | http://internet-apps.blogspot.com

  standards. innovation.
Received on Thursday, 20 December 2007 13:15:02 GMT

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