Where do you look and how do you determine deep vs. shallow body? My guess is that you look at the distance between withers and the bottom of the rib cage. Is it correct? So, the longer the distance--the deeper the body?
Ok, I found what I was looking for. In case you're interested:
"Body depth should be measured vertically through the head of the ninth rib or the tip of the sternum, not just behind the elbows.... The brisket line should run parallel to the ground back to the base of the eigths or ninth rib." The Dog in Action, p.33.