Here's a brief doc covering a conference in UK 04 comparing and contrasting different approaches to Assessing Risk in trees. It has three of the key Arb fellas in UK laying out their approaches, and yes there is a bit of jargon in there

but it really is crucial to understand where our starting point for determining whats acceptable risk and what is not.
Treeline04_Content.pdf
Too many of us have seen tree inspections resulting in unnecessary expensive work based on the individual quirks of a minor official, or worse dangerous collapsing trees left in areas with high target occupancy.
SF