working with the joint often you would renormalize as you work along so just say okay I have maybe currently my this thing is really a joint with all past evidence but I can also just renormalize it and forget about it being a joint and just say hey I'm just going to renormalize and know that it's now a conditional instead of a joint what do you lose you lose that probability you don't know anymore the probability of all the evidence you just have a conditional now for x2 or whatever time slice it is given everything else if you do care