My application sends an acknowledgement to an A&C alarm in a UA server. It does this by calling the method, MethodIds.AcknowledgeableConditionType_Acknowledge. This method has 2 arguments, the byte[] event ID and a string comment.

There is no argument to set the ClientUserId on the condition, so I cannot specify who acknowledged this alarm.

The spec indicates that ClientUserId is set by the session authentication. That produces some bad behaviour, like using the certificate subject name as the user ID. In any case, the session user is not necessarily the user name that I want. My application requires operators to log in to the application, separate from the back-end connection to the UA server, so I want the currently logged-in operator's name in the ClientUserId, not the session user.

The obvious resolution is to add an additional argument on AcknowledgeableConditionType_Acknowledge, or create an AcknowledgeEx method, so the caller can specify the acknowledger's name. That would also be more consistent with OPC A&E.