OPC 10000-5, Annex B.4.9 defines several ways of entering a SubStateMachine:

1. If the SubStateMachine has an initial state (i.e., a state of type InitialStateType) this state is entered whenever the parent state is entered.We make use of this principle for the VisionStepModelStateMachine defined in Section 8.4.
2. A SubStateMachine can also be entered by a direct transition from the parent state machine into one of its states, bypassing the initial state. In this case, the parent state machine goes automatically into the parent state of the SubStateMachine. We make use of this principle for operation mode state machines like the VisionAutomaticModeStateMachine defined in Section 8.3.
3. If a SubStateMachine has no initial state and the parent state is entered directly, the state of the SubStateMachine is server-specific.We make use of this principle for the error handling described in Section 8.2.2.4.