Collaboration of Opensocial apps via the Stream

Last week at IIW #8 Scott Seely, Martin Atkins and myself worked to add the hooks to the Opensocial APIs (0.9) in order to facilitate developers adding the full fidelity version of their activities into the stream.

The results of our collaborative brainstorming is here:
http://wiki.activitystrea.ms/OpenSocial-Activity-Publishing-Integration

The main concept behind this was to allow developers to reference an optional tranformation bundle which maps the fields in the activity raised to the proper objects in activitystrea.ms like for example the author, verb, object type and most importantly all the properties of such object: unique id, name, annotations, url, thumbnail, etc

The main pros of this approach is that it allows for the activitystrea.ms standard to evolve orthogonally.

All this led me to thinking:
Could we in fact provide such flexibility to our app developers where their products (the activities) could cross reference one another ? After all the ids are gobally unique. WHy could we not have the activities from one app reference the object of another domain ?

Imagine this scenario:

John Mayer Vanderbilt show on May 22nd 2009 photo stream

• Deb loves the new look on John >> from IFan Just Now
• Monica is wondering why John takes so long ! >> from Ticketberry 2 minutes ago
• John is getting ready to go on stage >> from IRockstar 4 minutes ago

Similar effects have been achieved with machine tags however there is no need for that given that the activities stream provides global unique identifiers. Surely one can produce a consumer which can leverage this and properly group based on the object id ?