RE: [xml-dev] What is the rule for parsing XML in a namespace inside HTML?

["Joshua Allen" <joshuaa@microsoft.com>]

> VML doesn't use the <xml> tag.  It uses the namespace decl 
> and a behavior CSS decl.  
> The solution needs to work from
> those declarations, not a tag.  OTW, the right way would be 

Well, this is why I think the <xml> tag is a better solution, though.  I
don't see why VML could not have done that.  Specifying namespaced
markup (or really, any XML) directly in an HTML 4.x document is a design
flaw, IMO.

> to insist when a namespace is embedded, that the wrapper 
> document (HTML in this case) be conformant XML even if it 
> isn't XHTML should the developer insist on 
> well-formedness.   We don't need more hacks. 

This is not a bad idea.  The main issues I see here are:
A) It's a retroactive spec change for HTML user agents.  As far as HTML
4.x spec is concerned, a namespace decl is no different from any other
attribute.  So you would either have to change the spec, or come up with
a new spec for a class of "xml-aware HTML user-agents".
B) It's quite likely that the majority of web pages that contain VML are
*not* wellformed.  For example, people use <link> tags or <p> tags that
are not closed.  So even a change to the "xml-aware HTML user-agent"
behavior could be a breaking change for many users.

Also, if I were to write a spec for a class of "xml-aware HTML
user-agents", my strong preference would be to go with the <xml>
convention.  Then from that, spec how user-agents validate the contents
of <xml> block.  I think the <xml> block could have been a really nice
convention for plugging in extra validation, registering plugins based
on namespace, etc.

> What happens when we get to XAML?

This is the other side of the coin.  In the case of XAML and WordML,
both of which can contain VML, the envelope already *is* XML, and is not
processed by an HTML browser.  The user-agent is already operating in
draconian mode.  So in that case, the <sml> convention would be
unnecessary (and in fact non-wellformed).