A similar problem exists in modern video codecs. You want to update the decoder with diffs based on some shared state. The problem is you don't really have "act

A similar problem exists in modern video codecs. You want to update the decoder with diffs based on some shared state. The problem is you don't really have "actions" you can do. You can say "start with this key frame" and then "this macroblock moved to here" but the fine detail of the change is likely unique and you need to send that diff explicitly.