5.1 JID vs Component Thing Registries
A client must treat the connection between a Thing Registry differently if it is hosted as a client, having a JID, or if it is hosted as a Jabber Server Component. If it is hosted as a server component, there's no need for the thing to become friends with the Thing Registry. Messages and requests can be made directly to the server component without having to add it to the roster or request presence subscriptions. If the Thing Registry is hosted as a client, having a JID (@ in the address), the Thing Registry must be added to the roster of the client before the client can communicate with the Thing Registry.