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Re: XHTML 2.0 - 3.2 Conformance Requirements (PR#7651)

From: Jim Ley <jim.ley@gmail.com>
Date: Thu, 26 May 2005 23:43:09 +0100
Message-ID: <851c8d31050526154366d0e334@mail.gmail.com>
To: w3c-html-wg@w3.org
Cc: www-html-editor@w3.org

On 5/25/05, Shane McCarron <shane@aptest.com> wrote:

I note this was sent to a member confidential list, please in future
archive responses to the issues I have raised to the public member
list, I do not feel bound by the implied member confidentiality in the
email, so I'm adding www-html-editor.

> > What does the first criteria mean?
> >
> > | The user agent must parse and evaluate an XHTML 2 document for
> > | well-formedness. If the user agent claims to be a validating user
> > | agent, it must also validate documents against a referenced
> > | schema according to [XML].
> >
> > It doesn't say anything about what should happen if the UA finds a WF
> > or schema violation.  What should happen?
> XHTML defers to XML for well formedness and validity checking. 
> XML leaves this up  to the implementation, so we do too.

Please change the document to include this information, currently it
is not specified at all, I do not accept this response as sufficient,
indeed I do not believe it answers the issue at all.

However, if the case is that the document will state that tehre is no
defined error processing for invalid and non-well-formed content, then
this is not acceptable to me, user agents cannot interoperate in any
way in this situation - see similar issues raised by many other groups
against numerous W3 specifications, the arguments are the same.

> > The 7th criteria, if standalone="yes" was set, this would be a WFness
> > error, does this criteria describe error recovery, or is this
> > behaviour only for non-standalone XML documents where the entity may
> > have been set in the external subset?
> We are not saying that external subsets have to be used.  An 
> implementation may, for example, have arcane knowledge of 
> popular general entities.

So a document that is not-well formed must still be rendered correctly
by an XHTML 2.0 user agent?   I understood from your previous response
that XHTML defers to XML in such respects, I understood XML said
normal processing could not continue - this appears to be incompatible
with your previous response.  I also reject this response as it
appears to be technically unsound.

>  All constraint
> 7 is meant to say is that if, for example, there is no font representation for a
> character, the user agent needs to do something to indicate there is a character
> there.

Please clarify constraint 7 to actually say this, as it is not clear
that it actually says this now.

> > 10.  Why MUST user agents use a particular visual representation if
> > they do not support CSS, and why is this restriction only on visual
> > presentation, (there are aural CSS settings in the default
> > stylesheet.)
> >
> > I don't see the need on placing any restriction on what a conforming
> > UA may do - I certainly do not agree with making a UA non-conforming
> > purely because it doesn't implement CSS and allows users to pick their
> > own colours for links!  (I realise that 10 only says SHOULD, but the
> > introduction to 3.2 says MUST.)  In any case I don't even agree that
> > this is a SHOULD for a conforming UA.
> HTML has traditionally described default presentational behavior.

Could you point me to a previous HTML WG document that defined
presentational behaviour?

>  What we have
> done with XHTML2 is 1) described this behavior using a well defined standard
> (CSS) and 2) relegated those default presentation behaviors to an appendix.  

I cannot see how this is a response to my issue, and I therefore
reject it.  No text has been clarified, you have not explained why
it's appropriate to make a user agent non-conforming for allowing uses
to choose a colour for links.

>We agree that there are many audiences beyond visual user agents.

So please either provide required renderings for these other types of
user agent. Or note specifically in the specification that non visual
user agents are not required to render it in that way.

> > Does the Fragment identifier constraint mean that with mixed namespace
> > content, I cannot use the fragment identifiers of the other namespaces
> > in an XHTML document to identify part of an SVG image say?
> Any attributes of type "ID" are legitimate fragment identifiers. 

Where in the specification can I find this information?  I reject the
response to this issue as it has failed to respond to the issue,
you've merely provided some other explanatory information, the issue
was are SVG fragment identifiers - e.g. of the type
#svgView(viewBox(0,200,1000,1000)) legal or not in mixed namespace
documents?   I appreciate this may be the domain of the CDF WG,
however I feel it's important that XHTML 2.0 does not restrict the
possibilities for interopability in mixed namespace content.

> > Is processing children of unknown elements sensible - this is what led
> > to the script cargo-cult of -- hide from old browsers gobbledygook.
> The purpose of child content rendering is to enable extensibility without
> breaking compatibility with legacy browsers. 

This is not true though, the example of SCRIPT and STYLE from HTML are
good examples of why it's not appropriate.  Or of course Bjoern's
example with SVG.  I reject this response and believe good technical
arguments of how child content rendering specifically breaks
compatibility have been given.     I reject this comment, please
change the specification in line with the original comment and
disallow child content rendering.

> > Also what happens with a mixed namespace document where you have an
> > SVG fragment with embedded XHTML2 inside a foreignObject, in what
> > situations should the XHTML portions be rendered - does the combined
> > document really make "sense" without the SVG elements, or will this be
> > simply forcing authors to go to extreme lengths to ensure their
> > documents degrade.  I feel the exact opposite of the above conformance
> > requirement would make more sense.
> Well - this situation is different.  Here you are talking about XHTML being used
> in a different host language.  In that situation, the conformance rules of that
> host language would kick in.

I am sorry if I was unclear, the host language was XHTML 2.0,
something of this sort of structure:

<html ...xmlns="http://www.w3.org/2002/06/xhtml2"  >... <svg
...xmlns="http://www.w3.org/2000/svg"> ... <foriegnObject><html ...
xmlns="http://www.w3.org/2002/06/xhtml2" >

The point being that there are XHTML 2.0 elements within elements of a
namespace that are not understood, my concern in the issue is that by
rendering the XHTML 2.0 elements inside the SVG fragment the meaning
of the document will change, and that in such a case we do not have
acceptable compatibility with XHTML 2.0 only user agents.   I
therefore reject the response to the issue, perhaps that was because
it wasn't clear, in which case please raise another issue.


Received on Thursday, 26 May 2005 22:43:13 UTC

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