Since there was so much interested in Benson's Unconditional Life algorithm,
that I thought some member of this list might be interest in another paper
by Martin Muller called Playing it Safe: Recognizing Secure Territories in
Computer Go by Using Static Rules and Search. He extents Benson's algorithm
by finding safety by locally alternating play and nonlocal safety by two
sure liberties. I know it's up on a web site somewhere but I can't find it
anymore. If anyone wants a copy, let me know and I'll e-mail it to you.