You can use it as the basis for earned value computations but be very
careful - it is an incredibly loosey-goosey kind of metric. If my task is
to lay 100 bricks into a walkway and I've laid 50, I'm 50% phyiscal
complete. Straight forward. But what if my task is to design an engine,
just what visible evidence will I have that I'm 50% physical complete? Half
the drawings? Crankcase done but still working on the cylinder head? Fuel
and electrical done but still working on the fuel and lube systems? It's a
concept that usually is extremely hard to pin down with any real accuracy.
