XML5
Anne van Kesteren: One of my side projects is XML5. Earlier this year I suggested the idea as XML 2.0, but in line with recent “jokes” about HTTP5, SVG5, and CSS5, XML5 makes perfect sense. The idea of XML5 is to provide a revision of XML 1.0, XML 1.1, Namespaces in XML 1.0, Namespaces in XML 1.1, and RFC 3023, that is backwards compatible and introduces HTML-like, although much more sane, error recovery.
Question: should XHTML5 be based on XML5 or XML1?
Warning: brainstorming ahead. Don’t groan.
Supposed HTML5 defined not one, and not two, but three serializations. The first one would be identified by the MIME type of text/html. The second one by application/xhtml+xml. The third one by a MIME type of text/html; subtype=xml.
General purpose browsers like Mozilla could support all three. Special purpose browsers may choose to only support fewer parsers. In particular, applications that require streaming support may chose to not implement the first type, and truly micro browsers may chose not to implement the first two (accepting some loss of fidelity in rendering some web pages).
Those that wished to include SVG or MathML inside of otherwise valid, but not well formed HTML pages, could do so with either a minor change to the MIME type or the addition of a <meta> tag. IE would continue to ignore these elements, but at least authors wouldn’t have to do heroic acts in their .htaccess files any more. And should IE ever wish to join the party, Microsoft would have the opt-in switch that they were looking for.