These are two experiments in which the robot performs sensing actions to verify whether a door is open. Sensing actions do not change the state of the robot in the environment, but affect the robot's knowledge about the environment. In this examples the initial state of the robot does not contain any information about doors. The planning system is able to generate a conditional plan involving sensing actions. When the plan is executed, the additive knowledge coming from results of sensing actions is used to decide which actions are to be executed in order to reach the room.
First case: The upper door is open.
Second case: The upper door is closed.