so smoothing now we care about let me try out here the context we will have x2 again and after the Y should be x3 and x4 and there will be observations Z for Z 3 Z 2 and I should all be things before it also x1 x0 and observation z1 c0 now we're just it in the distribution for x2 given all observations this is something you can do after the fact I have the fact analysis what happened to my system now to have all the information available so the quantity we're after is P x2 given Z 0 Z 1 Z 2 Z 3 Z 4 now again we know this is