Annex D (informative) Mapping from OPC A&E to OPC UA A&C ToC Previous Next

D.3 Alarms and Events COM UA proxy ToC Previous Next

D.3.7 Browse mapping ToC Previous Next

A&E COM browsing yields a hierarchy of areas and sources. Areas can contain both sources and other areas in tree fashion where areas are the branches and sources are the leaves. The A&E COM UA Proxy relies on the “HasNotifier” Reference to assemble a hierarchy of branches/areas such that each Object Node which contains a HasNotifier Reference and whose EventNotifier Attribute is set to SubscribeToEvents is considered an area. The root for the HasNotifier hierarchy is the Server Object. Starting at the Server Object, HasNotifier References are followed and each HasNotifier target whose EventNotifier Attribute is set to SubscribeToEvents becomes a nested COM area within the hierarchy.

Note that the HasNotifier target can also be a HasNotifier source. Further, any Node which is a HasEventSource source and whose EventNotifier Attribute is set to SubscribeToEvents is also considered a COM Area. The target Node of any HasEventSource Reference is considered an A&E COM “source” or leaf in the A&E COM browse tree.

In general, Nodes which are the source Nodes of the HasEventSource Reference and/or are the source Nodes of the HasNotifier Reference are always A&ECOM Areas. Nodes which are the target Nodes of the HasEventSource Reference are always A&E COM Sources. Note however that targets of HasEventSource which cannot be found by following the HasNotifier References from the Server Object are ignored.

Given the above logic, the A&E COM UA Proxy browsing will have the following limitations: Only those Nodes in the UA A&C Server’s address space which are connected by the HasNotifier Reference (with exception of those contained within the top level Objects folder) are considered for area designation. Only those Nodes in the UA A&C Server’s address space which are connected by the HasEventSource Reference (with exception of those contained within the top level Objects folder) are considered for area or source designation. To be an area, a Node shall contain a HasNotifier Reference and its EventNotifier Attribute shall be set to SubscribeToEvents. To be a source, a Node shall be the target Node of a HasEventSource Reference and shall have been found by following HasNotifier References from the Server Object.

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