The NodeIds of the Types defined in this specification are mandatory and fixed in the provided XML-file. This applies only to the Types themselves and not to the child elements. NodeIds of generated instances are not fixed and assigned by the individual OPC UA server. Therefore, the namespace of the NodeIds is the Local Server URI with namespace index 1 or a vendor specific namespace with vendor specific index. However, a Server shall persist the NodeIds of the generated Nodes, that is, it shall not generate new NodeIds when rebooting.
NOTE: It is not mandatory that the servers of all machines from one manufacturer use the same NodeIds for the individual instances, so a client cannot expect this. Also, a software update of a machine may lead to new NodeIds.