I hadn't really thought of it before, but essentially, Activity Streams is RSS or Atom on steroids. It is effectively the JSON-LD version of these formats. I mean this in the sense that it provides a stream of content (or "actions") in a machine-readable format.
Simplifying it down, helps a lot. It's probably not necessary to build an entire triplestore in Drupal. I imagine it would be simpler to provide a mapping to/from Activity Streams.
