Re: Minutes for July 30th, 2009 RDFa Telecon

Martin McEvoy wrote:
> 
> ...
> 
> Is there anything wrong with using xmlns: in the way I have proposed 
> above?  as I am unsure of what the Issues may be?, I think structure an 
> content are more clearly defined....? also xmlns is not depreciated in 
> html5 so really what's the cost?

HTML 5 (in its text/html serialisation) currently doesn't allow xmlns: 
to be used in that way. The only thing it allows is 
xmlns="http://www.w3.org/1999/xhtml" on an HTML element, and a few 
special cases in inline MathML/SVG content. Anything else is invalid.

It's unlikely that HTML 5 would allow xmlns: (or any other attribute 
name containing a colon) in valid documents, because it would either 
encourage violation of the "DOM Consistency" principle 
(http://www.w3.org/TR/html-design-principles/) or would risk violating 
"Support Existing Content".

(Web browsers parse xmlns:prefix="..." in text/html as an attribute with 
local name "xmlns:prefix" in no namespace, whereas XML parsers give it 
local name "prefix" in the XMLNS namespace, hence the DOM inconsistency 
(which affects namespace-aware DOM APIs, CSS selectors, etc), so people 
should be discouraged from using syntax with unexpected behaviour like 
that, to avoid making the language more confusing than it already is; 
and changing text/html parsers to be consistent with XML would break 
some current pages that rely on the current behaviour.)

-- 
Philip Taylor
pjt47@cam.ac.uk

Received on Wednesday, 5 August 2009 14:12:35 UTC