The HasNotifier ReferenceType is a concrete ReferenceType and can be used directly. It is a subtype of HasEventSource.
The semantic of this ReferenceType is to relate Object Nodes that are notifiers with other notifier Object Nodes. The ReferenceType is used to establish a hierarchical organization of event notifying Objects. It is a subtype of the HasEventSource ReferenceType defined in 7.16.
The SourceNode of this ReferenceType shall be Objects or Views that are a source of event subscriptions. The TargetNode of this ReferenceType shall be Objects that are a source of event subscriptions. A source of event subscriptions is an Object that has its “SubscribeToEvents” bit set within the EventNotifier Attribute.
If the TargetNode of a Reference of this type generates an Event, then this Event shall also be provided in the SourceNode of the Reference.
An example of a possible organization of Event References is represented in Figure 27. In this example an unfiltered Event subscription directed to the “Pump” Object will provide the Event sources “Start” and “Stop” to the subscriber. An unfiltered Event subscription directed to the “Area 1” Object will provide Event sources from “Machine B”, “Tank A” and all notifier sources below “Tank A”.
Figure 27 – Event Reference Example
A second example of a more complex organization of Event References is represented in Figure 28. In this example, explicit References are included from the Server’s Server Object, which is a source of all Server Events. A second Event organization has been introduced to collect the Events related to “Tank Farm 1”. An unfiltered Event subscription directed to the “Tank Farm 1” Object will provide Event sources from “Tank B”, “Tank A” and all notifier sources below “Tank B” and “Tank A”.