There were considerable discussions on the details of the API to be used when combining ActivityStreams with Open Social. With Open Social 2.0, Activity Streams has been included and it is possible to work from a single reference point. However for completeness we include the Activity Streams specification links here, as this still remains a separate and active standard. It is also worth noting that in IBM Connections we have adopted a number of proposed standards that are not yet fully accepted but are required in order to fulfuill our use cases.
The JSON format for Activity Streams is now the definitive one as Atom has been largely de-prioritied by both specification bodies (officially deprecated by Open Social).
Embedded Editing is not yet covered by ActivityStreams but is instead an active proposal
Other specifications and proposals of interest