According to the definition of the status OutOfService of the "#\MachineryBuildingBlocks\MachineryItemState" in the companion specification (https://reference.opcfoundation.org/Machinery/v102/docs/12) the machine needs to set this value if it is in an error or it is blocked.

If we now consider the use case that the system is used with an automatic loading system, the machine is internally blocked intentionally during loading process. The status OutOfService would not be correct. For our opinion the right status would be NotExecuting, since it is a wanted blocking of the machine and not an error.

The same question arises, if the system is loaded manually and the user opens the door to the system. The machine is blocked during the loading and can only be used after closing the door and restarting the process.

For "#\Production\ActiveProgram\State\CurrentState" (https://reference.opcfoundation.org/MachineTool/v101/docs/8.4.8) we see the same analogy regarding the state "Interrupted". The state Interrupted is basically only if the system was running in the state Executing. Otherwise the correct state would be Ended.

What is the correct behaviour?

The same situation is given for systems which are using a light barrier instead of a door. If the light barrier is triggered while the system is in the status Executing, cause the it needs to be loaded, which is a part of the normal operation mode.  What is the right status to switch into: OutOfService or NotExecuting?