I might not be communicating clearly either, but it’s a consistency thing. The intended usage I’m advocating for is to “make it an actor” by giving it an inbox and outbox, but also to go further and make self-managing collections that are attributed to themselves and Add objects into themselves. You can make the outbox private but you probably don’t want to. I don’t really see why to leave it out unless you were really adamant that the collections wouldn’t be actors. And if you go as far as I’m proposing with self-managing collections, then those are more clearly actors because they will be the actor of the Add activity. But also, you don’t have to go that far to just stick an outbox on it.