I'm to the point with this protocol where I have to define nuts and bolts and like.
Which is better?
```
Listen {
DocumentRef
}
```
or
```
Add {
Listener {
DocumentRef
}
}
```
Given that I am treating activities as ephemeral I suspect I am going to end up with the latter more than the former, but chewing on it.
Really fundamentally it's more a question of how to represent capabilities.
Because the easy model is to say that listenable objects contain a Listeners collection on them, and then you can, as an actor, Listen to a given object and get added to its listener list.
So that would look like this:
```
Add {
Actor,
DocumentRef.ListenerCollection
}
```