This Clause defines ReferenceTypes that are needed beyond those already specified as part of OPC 10000-3 and OPC 10000-5. This includes extending TwoStateVariableType state machines with sub states and the addition of Alarm grouping.
The TwoStateVariableType References will only exist when sub states are available. For example, if a TwoStateVariableType machine is in a False State, then any sub states referenced from the True state will not be available. If an Event is generated while in the False state and information from the True state sub state is part of the data that is to be reported than this data would be reported as a NULL. With this approach, TwoStateVariableTypes can be extended with subordinate state machines in a similar fashion to the StateMachineType defined in OPC 10000-5.