[whatwg] Supporting MathML and SVG in text/html, and related topics

Maciej Stachowiak mjs at apple.com
Wed Apr 16 10:22:16 PDT 2008

On Apr 16, 2008, at 9:36 AM, William F Hammond wrote:

> About 7 years ago there was argument in these circles about whether
> correct xhtml+mathml could be served as text/html.
> As we all know, a clear boundary was drawn, presumably because it
> was onerous for browsers to "sniff" incoming content and then decide
> how to parse.
> As things have evolved, we now know that browsers do, in fact, perform
> a lot of triage.  See, for example, "Mozilla's DOCTYPE sniffing",
> http://developer.mozilla.org/en/docs/Mozilla's_DOCTYPE_sniffing
> Especially since we are speaking about dual serialization of the same
> DOM and since there is relatively little use of
> "application/xhtml+xml" (and some significant user agents do not
> support it), might it not be worthwhile to re-examine the question of
> serving standards-compliant xhtml or xhtml+(mathml|svg) serialized
> document instances as either "text/html" or "application/xhtml+xml"?
> In other words, why not be able to serve both serializations
> as "text/html"?
> What obstacles to this exist?

It's not entirely clear what your proposal is, but I assume you are  
suggesting that content served as text/html with an XHTML doctype  
declaration should be parsed as XML. The obstacle to this is that much  
text/html content has an XHTML doctype declaration but depends on  
being parsed and otherwise processed as HTML, not XML, as current user  
agents do it. Such content is fairly widespread due to the legacy of  
Appendix C. It is preferable to let the MIME type continue to be the  
switch rather than making the doctype serve this role.

An additional obstacle in the case of HTML5 is that the XML  
serialization does not have a distinct doctype (they may use the  
common HTML5 doctype or no doctype at all, which when parsed as text/ 
html would be treated as an HTML document in quirks mode).


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