Back in July of 2008 I started thinking about HTML microformats for linking together and discovering social objects on the web.
I later discussed this with folks at the Internet Identity Workshop and after a few rounds of discussion we ended up working on Activity Streams instead, which shifted the focus to machine-readable descriptions of actions on social objects. However, the social object research here was the initial basis of what went on to become the "Object Types" in Activity Base Schema, after many iterations.