right any questions about this then let me project in typeset lay tag the equations we just derived by example on the board but we're going to look at see how these on the slides this is what we did we did this the whole smoothing thing this is the full filter equations at the bottom going to magnify them there's a backward and a forward we can combine them to get the local so here's the full thing we can run a filter forward and we'll call those things a messages in some sense indexed by time so very simple set of update equations