@Gaba
gaction is just trigger definition about your voice query (and the simple response - If you need more complex response, you should have at least one server which fulfill your response on realtime)
It means, you can make voice order “Open the door”, and you can make GA response like “Yes, sir” with gAction,
but the real action of opening door should be made by yourself(or by other program). See the command and gAction sections in documents. command would do real job.