Assuming that some PubSubConfiguration already exists on the AutomationComponent, and that the next UAFX connection to be established will require inserting elements under the existing PubSubConnection object. Assuming also that this existing PubSubConnection object has the PublisherId set, which is pre-engineered i.e. set to a value other than DefaultPublisherId.

See the following workflow:

In the 1st step of EstablishConnections CM uses the ReserverdIds command. In a response to this call, a default PublisherId shall be returned as per Part 14 - [9.1.3.7.5 ReserveIds Method].

Then the reserved IDs are used by the CM to prepare PubSubConfiguration that is going to be applied in the 2nd step.

In the 2nd step of EstablishConnections CM uses the SetCommunicationConfiguration command. CM sets the ConfigurationReferences (PubSubConfigurationRefDataType) such that for PubSubConnection element the Add&Match action is specified. Assuming that the match was true, in a response to that call AC returns the PublisherId that was originally set (pre-engineered) for the PubSubConnection.

Now CM may recognize that there is a problem!

Previously it used the DefaultPublisherId returned from ReserveIds to prepare the rest of PubSubConfiguration. But now, it realizes that the actual PublisherId is different. The PubSubConnection that just got applied will not work.

This situation needs a special handling on the CM side, which shall be explained in the annex. Generally is should be recommended to always use the DefaultPublisherIds for PubSubConnections.