intertwingly

Mark Nottingham: How would we do this for RSS? I think it would be relatively easy (and MUCH more lightweight). Get a bunch of aggregator folks (virtually) together and decide what features they're going to support - e.g., xhtml:body, how to interpret markup inside description, how to prioritize different elements that do the same thing, etc. Use Jorgen's RSS schema, and modify it to make it easy to validate a profiled feed.

I can help.  For starters, here's a regex that the rss validator uses for rfc822 + Y2K formatted dates:

^(((Mon)|(Tue)|(Wed)|(Thu)|(Fri)|(Sat)|(Sun)), *)?\d\d?
+((Jan)|(Feb)|(Mar)|(Apr)|(May)|(Jun)|(Jul)|(Aug)|(Sep)|(Oct)|(Nov)|(Dec))
+\d\d(\d\d)? +\d\d:\d\d(:\d\d)?
+(([+-]?\d\d\d\d)|(UT)|(GMT)|(EST)|(EDT)|(CST)|(CDT)|(MST)|(MDT)|(PST)|(PDT)|\w)$