An OPC UA session is interpreted as a single transaction according to the invention. In this case, a transaction means that all service calls, apart from the abovementioned calls, are initially only simulated and are not executed and the execution of the service calls is shifted to the termination of the transaction. Each operation inside a session is formally checked and then simulated. The simulated result or the result of the formal check is immediately sent to the client. The client therefore receives a preview of the result of the operations. If the client determines that one of the operations carried out would not lead to the desired result, the client can reject the operations. If the client wants the set operation to be carried out, the client terminates the current session.