@smallcircles @steve I think the one thing that's interesting in what you've said is determining if a server will manage the side-effects expected when you send an activity to an `inbox` or `outbox`. For example, if an actor posts an `Arrive` activity to their `outbox`, will the server automatically update the actor's `location`? I'd answer, design extension vocabularies such that there is a reasonable fall-back if the server doesn't implement side effects.