6 General requirements

6.1 NodeIds

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.

6.2 AnalogItemType

For this specification, wherever AnalogItemType is used, the property EngineeringUnits is mandatory. The unit system described in OPC UA Part 8 (“Codes for Units of Measurement (Recommendation N°. 20)” published by the “United Nations Centre for Trade Facilitation and Electronic Business” (see UN/CEFACT)) shall be used.

6.3 EventNotifier

If events are supported, the root node of the specific interface (e.g. IMM_MES_Interface for OPC 40077) shall set the SubscribeToEvents flag in the EventNotifier attribute.

If event history is supported, the root node of the specific interface (e.g. IMM_MES_Interface for OPC 40077) shall set the HistoryRead flag in the EventNotifier attribute.

6.4 Severity of events

Wherever a Severity property is used (e.g. in MESMessage in 14.4, all events based on BaseEventType), the following classification shall be used: