User Authenticationis achieved when the Clientpasses user credentials to the Serveras specified via Session Services(described in OPC 10000-4). The Servercan authenticate the user with these credentials.

The owner (user) of a Session can be changed using the ActivateSession Servicein order to meet needs of the application.

User Authenticationis not directly part of the Publish-Subscribecommunication pattern but is used as part of the SKS associated with this communication pattern.