I wouldn't be opposed to renaming `activityStreamId` to `streamType` as that would bring the whole thing in line with activity routes. (An activity route is essentially a tuple of `activityStreamId` and `streamType`.)

I'm not too sure about channels. Initially, I started out with something like that and we eventually decided to keep everything tied to activities. Since the Push utility only publishes routed activities and you can only route to "resources" I'd like to keep it as `resourceId`.