Brion said: /It doesn't solve our specified requirement (single Wikimedia-wide namespace so a single username works on all 600+ Wikimedia wikis transparently, no muss no fuss). / Really? I'd think that an Interwiki-namespaced username would solve that problem nicely, without requiring a big name-clash-fixing step when the technology rolls out. I think that having a single username across all wikis would be nice, if you didn't have to do resolve dupes across the system, but if you do, it's really kind of a hassle. I'd think that, since single-signon between wikis is a feature useful only for a minority of registered Wikimedia users (how many actually log into more than one Wikimedia wiki, ever? 10-20%, maybe? how many log into more than, say, 5 wikis? Or log into more than one wiki on a regular basis? 2%? 0.2%?), it'd be a good political idea to minimize the namespace-sorting hassle. That nameclash-fixing step is gonna suck, and it's not even helpful most users. It seems to me that a minor effort on the part of "interwikiists" -- just using a project+language namespace -- would be painless for them and unnoticeable for everyone else. I think that if we use Interwiki prefixes on the UI side, OpenID becomes that much easier. A user could login to French Wikibooks as /wp:en:User:EvanProdromou/ or whatever, and the UI translates that into the right OpenID URL (http://en.wikipedia.org/wiki/User:EvanProdromou) and goes through the OpenID two-step to get credentials checked. Under the covers, the OpenID stuff would get worked out right, but we could use simpler Interwiki strings for the UI. In fact, a drop-down box for project, and another for language, could also significantly reduce the complexity for users. For example, I could choose "Wikipedia" out of "Wikipedia, Wikibooks, Wiktionary, ..." and "English" out of "English, Français, Esperanto, ..." and then my username on that project. Lastly, I think having a couple of professional developers eagerly awaiting a chance to get this implemented and who know OpenID and authentication issues inside and out is a really good thing. We shouldn't rollout every technology that people volunteer to throw into the software, but this seems like a pretty good match between Mediawiki (and Wikimedia) needs and what's being offered. ~Evan P.S. Sorry about the broken threading -- I had some mail server problems and missed my daily dose of wikitech-l.