In discussing what goes with us on a trip, I understand that there are three accepted categories:
1. Items Worn or Carried, like shoes, GPS around your neck, wedding ring
2. Items carried in your pack, not consumed during the trip. Shelter, sleep system, and the pack itself comprise the "Big 3."
3. Consumables, including food, water, water treatment, fuel
From those weights, two others can be calculated:
Initial Pack Weight = 2 + 3
Skin Out Weight = 1 + 2 + 3
That's what I've gathered, at least. And yes, base pack weight does include the weight of the pack.