Anne van Kesteren: The time has probably arrived to define graceful error handling for XML, put some IETF, W3C or WHATWG sticker on it, label it XML 2.0 and ship it. Perhaps we can drop this internal subset thing in the process.
I’ve been slowly but steadily prototyping this in the html5lib svn repository. Since this post, I’ve added both W3C DOM support and can produce SAX2 events (with or without namespaces) from that DOM. A SAX w/namespaces interface will make it easier for me to replace sgmllib as the fallback in the event of XML parsing errors in the Universal Feed Parser.