I always used invasion square (or convergence square) in stead of focal point in the past, btw.
When I tested the system we are trying to develop against practice, I noticed that we might count at the wrong moment. I started with counting right away when I look for domination squares. The reason for this is that I want to prune squares which there might be a contact, but which are not interesting. But look what happens in this position when you start counting:
|black to move|
Domination squares: f3, f1, d3, g3
Invasion square g4
If I count the situation on f1, then it is attacked twice and defended four times, so it scores minus two. But that score is irrelevant, since with two power moves, I can harass 3 of the 4 defenders. For instance: 1. ... g4 2.Nh4 Qxd3 3.Rxd3 winning the white rook at f1. This means it makes no sense to count before you consider the defenders and how to harass them. You can't prune anything based on counting for domination. Without counting for domination, you don't know whether you dominate a square. That makes the term "domination square" nonsensical. Maybe "contact squares" is a better term. That frees the D from Domination, which I can then use for Defender, the term that I am used to, in stead of Guard. Which reads M WIMP CID, which is a bit of a pity, since DIG is easier to remember than CID. But hey, it is a work under construction! We need to automate it anyway, so it is just a pair of training wheels.