Following are sub-types of SystemEventType that will be generated in response to a Refresh Methods call. They are illustrated in Figure 23.
Figure 23 – Refresh Related Event Hierarchy
This EventType is used by a Server to mark the beginning of a Refresh Notification cycle. Its representation in the AddressSpace is formally defined in Table 99.
Table 99 – RefreshStartEventType definition
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Attribute |
Value |
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BrowseName |
RefreshStartEventType |
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IsAbstract |
True |
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References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
ModellingRule |
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Subtype of the SystemEventType defined in OPC 10000-5, i.e. it has HasProperty References to the same Nodes. |
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This EventType is used by a Server to mark the end of a Refresh Notification cycle. Its representation in the AddressSpace is formally defined in Table 100.
Table 100 – RefreshEndEventType definition
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Attribute |
Value |
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BrowseName |
RefreshEndEventType |
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IsAbstract |
True |
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References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
ModellingRule |
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Subtype of the SystemEventType defined in OPC 10000-5, i.e. it has HasProperty References to the same Nodes. |
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This EventType is used by a Server to indicate that a significant change has occurred in the Server or in the subsystem below the Server that may or does invalidate the Condition state of a Subscription. Its representation in the AddressSpace is formally defined in Table 101.
Table 101 – RefreshRequiredEventType definition
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Attribute |
Value |
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BrowseName |
RefreshRequiredEventType |
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IsAbstract |
True |
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References |
NodeClass |
BrowseName |
DataType |
TypeDefinition |
ModellingRule |
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Subtype of the SystemEventType defined in OPC 10000-5, i.e. it has HasProperty References to the same Nodes. |
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When a Server detects an Event queue overflow, it shall track if any Condition Events have been lost, if any Condition Events were lost, it shall issue a RefreshRequiredEventType Event to the Client after the Event queue is no longer in an overflow state.