Add the Object Model page What an object is, the trinket/virtual split and why virtual types take no common properties, the single id space shared by both, the three ways to address an object, containment, and the top-level types. Documents what destroy actually does: it forgets the destroyed object's own key and nothing else. The subtree leaves the display with its parent, but every key surfaced below it still resolves and still accepts set, silently, against objects that can no longer be drawn.