W3C home > Mailing lists > Public > public-xml-versioning@w3.org > February 2007

Re: XHTML modularization and substitution groups (tag issue XMLVersioning-41, TagSoupIntegration-54, RDFinXHTML-35)

From: Chris Lilley <chris@w3.org>
Date: Thu, 15 Feb 2007 22:39:19 +0100
Message-ID: <558027612.20070215223919@w3.org>
To: Dan Connolly <connolly@w3.org>
Cc: public-xml-versioning@w3.org

On Thursday, February 15, 2007, 10:22:00 PM, Dan wrote:

DC> On Thu, 2007-02-15 at 18:02 +0100, Chris Lilley wrote:
>> Hello public-xml-versioning,
>> Dan wrote:
>> > I'm interested in a form of extensibility where a markup
>> > language designer can make a new my:box element and
>> > say "it's an HTML block element"; then, when a
>> > document containing a my:block element is checked
>> > for syntactic happiness, the checking tool uses
>> > normal HTML schemas until it gets to my:box; then
>> > it looks up my:box in the web, finds that it's
>> > declared to be an HTML block, and find than
>> > an HTML block is allowed here, and carries on happily.
>> Thats interesting, but it seems to assume a top-down model where
>> extensions are tightly bound to their expected environment. What if I
>> want to use my:box inside Timed Text, or inside SVG?

DC> Yes, I'm influenced by the "XML functions" idea that Tim
DC> has advocated in the context of a related issue that I
DC> neglected to mention...
DC>   http://www.w3.org/2001/tag/issues.html?type=1#xmlFunctions-34
DC>   -> http://www.w3.org/DesignIssues/XML

DC> It's largely top-down, i.e. compositional.

Yes. Which is why I was puzzled recently to hear 'top down' used as a
negative term, and used in opposition to 'Web-like'.

DC>  See
DC> also "4. Elaboration defined: top-down treewalk, signals and namespaces"
DC> in a recent draft by Henry Thompson.
DC>   http://www.w3.org/2001/tag/doc/elabInfoset.html

DC> I expect that the 'HTML block' concept (substitution group?) could
DC> be shared with Timed Text and SVG, though I haven't worked out any
DC> of the details.

I suspect you will find that it works sort of for TT, not at all for
SMIL, and only slightly for SVG.

Its another example of "it seems to work for HTML" != "works for any
generic XML".

I say "seems to" because it doesn't always work for HTML either. Lets
suppose HTML had no style element and no script element and I propose
to add them.

Suppose I tell you that cl:style and cl:script are html:block. Where
does that get you?

DC> [...]
>> I can point to some worked examples using RNG (and the same in DTD)
>> Here
>> http://www.rddl.org/xhtml-rddl.rng
>> is the schema for RDDL. It could hardly be simpler.

DC> If you have time to elaborate some other piece of the puzzle,
DC> I'd appreciate it.

I strongly suggest reading Robin Berjon's thoughts on composing
namespaces and designing schemas:


DC> I'd like to see how that schema is used with other schemas in
DC> a document.

DC> something analagous to one of these two...
DC> http://www.w3.org/XML/2000/04schema-hacking/xhtml-mathml-ex.html
DC> http://www.w3.org/XML/2000/04schema-hacking/comment-test.html

>> > I'm also interested in whether CDF/WICD can/should use substitution
>> > groups.
>> > http://www.w3.org/TR/WICD/
>> They decided to use NVDL and RelaxNG instead.

DC> Anybody have pointers to more details about that? I don't
DC> see "NVDL" in that particular tech report.

The first draft of CDI - Compound Documents by Inclusion - has not
been published. The question of composing multi-namespace,
multi-schema documents does not arise if they are only using linking
rather than inclusion.

Or were you asking for more details on NVDL in general?

 Chris Lilley                    mailto:chris@w3.org
 Interaction Domain Leader
 Co-Chair, W3C SVG Working Group
 W3C Graphics Activity Lead
 Co-Chair, W3C Hypertext CG
Received on Thursday, 15 February 2007 21:38:52 UTC

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