The HasNotifier ReferenceTypeis a concrete ReferenceTypeand can be used directly. It is a subtype of HasEventSource.

The semantic of this ReferenceTypeis to relate Object Nodesthat are notifiers with other notifier Object Nodes. The ReferenceTypeis used to establish a hierarchical organization of event notifying Objects. It is a subtype of the HasEventSource ReferenceTypedefined in 7.16.

The SourceNodeof this ReferenceTypeshall be Objectsor Viewsthat are a source of event subscriptions. The TargetNodeof this ReferenceTypeshall be Objectsthat are a source of event subscriptions. A source of event subscriptions is an Objectthat has its “SubscribeToEvents” bit set within the EventNotifier Attribute.

If the TargetNodeof a Referenceof this type generates an Event, then this Eventshall also be provided in the SourceNodeof the Reference.

An example of a possible organization of Event Referencesis represented in Figure 27. In this example an unfiltered Eventsubscription directed to the “Pump” Objectwill provide the Eventsources “Start” and “Stop” to the subscriber. An unfiltered Eventsubscription directed to the “Area 1” Objectwill provide Eventsources from “Machine B”, “Tank A” and all notifier sources below “Tank A”.

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Figure 27– Event Reference Example

A second example of a more complex organization of Event Referencesis represented in Figure 28. In this example, explicit Referencesare included from the Server’s Server Object, which is a source of all Server Events. A second Eventorganization has been introduced to collect the Eventsrelated to “Tank Farm 1”. An unfiltered Eventsubscription directed to the “Tank Farm 1” Objectwill provide Eventsources from “Tank B”, “Tank A” and all notifier sources below “Tank B” and “Tank A”.

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Figure 28– Complex Event Reference Example