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There are some draft specs on the activitystrea.ms site. FB seems to implement them in Open Graph.

http://activitystrea.ms/spec/1.0/ http://activitystrea.ms/schema/1.0/ http://wiki.developers.facebook.com/index.php/Using_Activity...

There are a few different standards, but I don't think it's achieved the level of a W3C style consortium. Google's been working on initiatives, and even Facebook is involved. Appleseed and Cliqset are two products which I believe already implement several protocols, while Diaspora is meant to do the same from what I've read.

They've been having discussions with various standards groups which I forget the names of at the moment.