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.3.1 General ToC Previous Next

As illustrated in the figure below, the A&E COM UA Proxy is a COM Server combined with a UA Client. It maps the Alarms and Conditions address space of UA A&C Server into the appropriate COM Alarms and Event Objects.

Subclauses D.3.2 through D.3.9 identify the design guidelines and constraints used to develop the A&E COM UA Proxy provided by the OPC Foundation. In order to maintain a high degree of consistency and interoperability, it is strongly recommended that vendors, who choose to implement their own version of the A&E COM UA Proxy, follow these same guidelines and constraints.

The A&E COM Client simply needs to address how to connect to the UA A&C Server. Connectivity approaches include the one where A&E COM Clients connect to a UA A&C Server with a CLSID just as if the target Server were an A&E COM Server. However, the CLSID can be considered virtual since it is defined to connect to intermediary components that ultimately connect to the UA A&C Server. Using this approach, the A&E COM Client calls co-create instance with a virtual CLSID as described above. This connects to the A&E COM UA Proxy components. The A&E COM UA Proxy then establishes a secure channel and session with the UA A&C Server. As a result, the A&E COM Client gets a COM Event Server interface pointer.

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