JapaneseRules/Life and Death

Sub-page of JapaneseRules

Because the Japanese rules make use of Traditional Territory Scoring, which penalizes plays in your own territory, they provide for resolving life and death questions at the end of the game without actual play.[1]

The 1949 Japanese rules, the first formally written Japanese ruleset, made first ad hoc attempts to define life, death, and territory. That and special rulings for peculiar shapes drew criticism.

The 1989 rules were an improvement in the sense that such cases are now decided by method. The drawback is that the method is not easy to understand. Besides the rules [ext] contradict traditional scoring even in basic shapes, according to Robert Jasiek.

See Question About Japanese Scoring for some discussion and Bent Four In The Corner for a scarce but frequently cited example.

If there is a necessity to clarify life and death after both players have passed, this is resolved by hypothetical play in which a ko ban on a particular ko may be lifted by a pass designating that ko.

Q and A

Exir: If there is disagreement about life & death, and it has to be settled by hypothetical play, who starts? What if a group is dead if white plays first, but alive if black plays first? Is that group dead or alive?

RobertJasiek: Read my commentary on the Japanese 1989 Rules; it answers most of your questions.

Bill: If it matters who starts, then the position should not be on the board at the end of the game. As for your example, the group is dead. But the fact that there is an effective play may make both players lose.

Exir: Hmmm... I don't quite understand this part of the rules {passing for ko}. What is the ko ban? Can anybody explain? And how does a pass designate a ko? Can anyone explain?

Bob McGuigan: "Ko ban" refers to the prohibition on retaking the ko without making a move elsewhere first. The idea is that a pass move could be used as the "move elsewhere". If there is more than one ko it seems it might be necessary to specify that the pass is used as a move for a particular ko.

Exir: Okay. I still don't quite understand: when the status of life and death of a group involves a ko (and possible ko fight), how do we determine the life and death? Or is it necessary to resolve the ko before scoring?

Bill: The basic idea behind the "pass for ko" rule is that at the end of the game life and death positions involving ko are resolved by (hypothetically) playing the ko with no threats. The pass for ko rule forces the player who takes a ko to resolve it (if possible); otherwise the defender can take the ko back. Under such play, if the result depends on who plays first, the ko should be resolved before the end of play. Otherwise both players may lose.

I discuss some official examples at Spight Japanese Style Rules/Commentary.

See Discussion for more.

[1] There are territory rules that provide for resuming play in an encore to resolve life and death, such as Lasker-Maas rules, Ikeda Territory I Rules, and Spight rules. Play in the encore uses area scoring, in effect. This allows a player to capture dead stones without penalty.

Harleqin: It is also possible to use a "virtual" encore, restoring the end position afterwards. That way, you do not revert to area scoring but still have no need for a definition of life and death. I have devised such a ruleset: Einfache Gebietsregeln.

JapaneseRules/Life and Death last edited by Bill on July 31, 2007 - 18:11
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