Only a single subscription is supported per NETCONF session as per section 6.5 of the NETCONF Event Notifications RFC (5277). A subscription is bound to a single stream as per section 2.1 of the NETCONF Event Notifications RFC (5277).
Can there be multiple notifications(with different XML formats) in one stream
Can the notification be triggered by calling a send_notification from the confd client, and will this be propagated forward. or does the confd server monitor the yang model for triggering this. (i want to send a notification northbound from the confd client independent of any leaf in the yang model )
You can use subtree or XPath filtering to specify the subset of all possible events that is part of the same stream, as per the Event Stream Definition in RFC 5277, to be sent. Only a single stream can be specified per session as was stated in my previous response.
Other than the default NETCONF stream, all other streams are to be triggered by the ConfD client applications using the confd_notification_send( ) API call as described in the ConfD User Guide.