I just had a thought (astounding!)
If we remove the version attribute and change the namespace only when there is a backwards incompatible spec revision, and assume mustIgnore for unrecognised elements from any minor version updates ... then this leaves the door open for someone to produce feeds with any ad hoc element, even elements which are not in any updated Atom specification. How would a feed validator react to something like this: <feed xmlns="http://purl.org/atom/ns#1.0";> <head>...</head> <entry> <foo>...</foo> ... </entry> </feed> It can't say <foo> isn't allowed in this feed, because it doesn't know if <foo> was introduced in Atom 1.1. If the validator is updated to know about Atom 1.1, the same problem exists: it doesn't know if it came from 1.2. One of the criticisms I've seen for OPML is that anyone can add any element or attribution of their own invention anywhere any time, and that this has led to xml-soup. Do we want to see the same future for Atom? e.
