OPC UA Objects that have the EventNotifier Attribute set to SubscribeToEvents are so called event notifiers. They can be used by OPC UA Clients to subscribe for Events from the OPC UA Server. The OPC UA ReferenceType HasNotifier is used to build an event notifier tree starting from the Server Object.
BACnetNotifierType Objects like instances of BACnetNotificationClassTypes are used together with instances of the BACnetDeviceType to represent the OPC UA event notifier hierarchy starting from the Server object.
Figure 12 shows an example of BACnet objects referencing each other with BACnetObjectIdentifiers and the representation with OPC UA Objects and References. The example contains a BACnet Device object, one Analog Input object that creates alarms and therefore references a Notification Class object.