Just to address the Pace. I support it, but I don't think it's necessary to add it to XML data types, since "normally [this would] mean that the "atom:content" element would contain a single child element which would serve as the root element of the XML document of the indicated type", which is where you put the namespace, so you'd never need a wrapper, so we can drop the attribute and assume its value is "none".
For XHTML, there's almost no reason not to add the div, so we might as well drop the attribute here and use assume its value is "dispose".
Handily this means your Pace can be implemented with no changes to the current draft.
Graham
