PubSuband Client Serverare both based on the OPC UA Information Model. PubSubtherefore can easily be integrated into OPC UA Serversand OPC UA Clients. Quite typically, a Publisherwill be an OPC UA Server(the owner of information) and a Subscriberis often an OPC UA Client. Above all, the PubSub Information Modelfor configuration (see 9) promotes the configuration of Publishersand Subscribersusing the OPC UA Client Servermodel.

Nevertheless, the PubSubcommunication does not require such a role dependency. I.e., OPC UA Clientscan be Publishersand OPC UA Serverscan be Subscribers. In fact, there is no necessity for Publishersor Subscribersto be either an OPC UA Serveror an OPC UA Clientto participate in PubSubcommunications.

More details on how Subscriptionsin the Client Servercommunication model compare to PubSubare described in Annex B.