JoeJ said:
An example: A group of NPCs has to enter a house. But an explosion has thrown a rock before the door.
That`s a very loose (vague) scenario, is it a physics driven game? If the purpose is to enter the house they must be `geared` to get any type of obstacle out of the way. Also 90% of AI is about movement. If you want them to cooperate (lift the boulder together) it`s about syncronisation of movement.