Here follow some additional thoughts
(largely based on 囲碁ルールの研究–理論と歴史 by 関口 晴利; "Research on Go Rules – Theory and History" by Sekiguchi Harutoshi, ISBN 978-4286031422) about the challenge to phrase an unambiguous rules text. To keep it relatively simple, a discussion on the application for complicated large formations with (several) open ko-shapes
is not included.
What do we "really" want by using Japanese style rules for eventually scoring the game ?
First we have to decide on "life and death", thereafter, we can decide on "prisoners" and "territory".
+ + + + + + + + + +
Let us start with groups that are "independently alive".
Type 1:Probably we would like to start with considering a group of black stones to be "alive" that surrounds two (or more) empty points of the board, which are "forbidden" for White.
- Click Here To Show Diagram Code
[go]$$B
$$ +-------------
$$ | C X C X O .
$$ | X X X X O .
$$ | O O O O O .
$$ | . . . . . .[/go]
Usually, these "forbidden-for-White" points are called black eyes, so let us call this type of life "2EL" (= two-eyes-life).
As a matter of course, groups of type 1 "cannot be captured". However, you will surely know that type 1 is not a unique application case for "cannot be captured".Type 2:Not everything on the board is yet solidly connected, so we have to include black groups that – even if White plays first – can be transformed into type 1, explained above, by using alternative play.
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | . X . X O .
$$ | X X . X O .
$$ | O X X O O .
$$ | O O O O . .
$$ | . . . . . .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | . X 2 X O .
$$ | X X 1 X O .
$$ | O X X O O .
$$ | O O O O . .
$$ | . . . . . .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | C X X X O .
$$ | X X C X O .
$$ | O X X O O .
$$ | O O O O . .
$$ | . . . . . .[/go]
Type 3:Not everything on the board is safe from being captured by the opponent, so we have to include a type of black groups that is mainly known from the "snap-back"-issue. Even if a black stone
(phrasing for a group would be more tricky) has been captured, it is said to be of the "2EL"-type, if Black can transform the before occupied point into an integral part of a black type 1 or type 2 group through alternative play.
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | O O X X . X .
$$ | . Y O X X X X
$$ | X O O O O O O
$$ | X X O . . . .
$$ | . X O . . . .
$$ | X X O . . . .
$$ | . X O . . . .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | O O X X . X .
$$ | 1 X O X X X X
$$ | X O O O O O O
$$ | X X O . . . .
$$ | . X O . . . .
$$ | X X O . . . .
$$ | . X O . . . .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | O O X X . X .
$$ | O 2 O X X X X
$$ | X O O O O O O
$$ | X X O . . . .
$$ | . X O . . . .
$$ | X X O . . . .
$$ | . X O . . . .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | . . X X . X .
$$ | . Y O X X X X
$$ | X O O O O O O
$$ | X X O . . . .
$$ | . X O . . . .
$$ | X X O . . . .
$$ | . X O . . . .[/go]
As a matter of course, in the overwhelming majority of cases this captured black stone will be replaced by a permanent stone of the same color. However, there are exceptions ...
- Click Here To Show Diagram Code
[go]$$W
$$ +-----------------
$$ | O Y . . X . X O .
$$ | . O X X X X X O .
$$ | X X X O O O O O .
$$ | O O O O . . . . .
$$ | . . . . . . . . .[/go]
You will surely agree that Black's marked stone is "alive". However, ...
- Click Here To Show Diagram Code
[go]$$W
$$ +-----------------
$$ | O Y 1 . X . X O .
$$ | . O X X X X X O .
$$ | X X X O O O O O .
$$ | O O O O . . . . .
$$ | . . . . . . . . .[/go]
... after White captured this stone ...
- Click Here To Show Diagram Code
[go]$$W
$$ +-----------------
$$ | O 3 O 4 X . X O .
$$ | 2 O X X X X X O .
$$ | X X X O O O O O .
$$ | O O O O . . . . .
$$ | . . . . . . . . .[/go]
... she is able to stop Black from re-occupying that point with a stone.
- Click Here To Show Diagram Code
[go]$$Wm5 W 7, 9 = pass
$$ +-----------------
$$ | 6 1 4 X X . X O .
$$ | X 2 X X X X X O .
$$ | X X X O O O O O .
$$ | O O O O . . . . .
$$ | . . . . . . . . .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-----------------
$$ | X C X X X C X O .
$$ | X X X X X X X O .
$$ | X X X O O O O O .
$$ | O O O O . . . . .
$$ | . . . . . . . . .[/go]
Effectively, this point will become a "forbidden-for-White"-point, i.e. an eye.
"... transform ... into an integral part of a type 1 or type 2 group" might be replaced by "... re-occupied by a black stone or turned into a point that is forbidden for White".+ + + + + + + + + +
Another cluster of groups consists of those groups which are
not part of "2EL", but are "alive in seki".
Please note that this second type of "life" is needed to get rid of the usage of "dame". Quite obviously, the authors of the J89 rules did not want to do so.Type 4:The simple case of "life in seki" ("LIS") contains black groups that – even if White plays first – can be prevented by Black from being captured by White by alternative play.
- Click Here To Show Diagram Code
[go]$$W
$$ +-----------------
$$ | . X O . Y O . O
$$ | X X O . Y O O .
$$ | . X O O O X O O
$$ | X X X X X X X O
$$ | O O O X . X . X
$$ | . . O O X X X .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-----------------
$$ | . X O 2 X O . O
$$ | X X O 1 X O O .
$$ | . X O O O X O O
$$ | X X X X X X X O
$$ | O O O X . X . X
$$ | . . O O X X X .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-----------------
$$ | . X . X X O . O
$$ | X X . . X O O .
$$ | . X . . . X O O
$$ | X X X X X X X O
$$ | O O O X . X . X
$$ | . . O O X X X .[/go]
Type 5:The challenging case (not very relevant for practical use) covers black groups that can be captured by White, but where after at least one point of the before occupied area can be transformed into an integral part of a black type 1 or type 2 group.
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | . Y Y O . .
$$ | O Y Y O . .
$$ | X O O O O O
$$ | X X X X O .
$$ | . X . X O .
$$ | X X X X O .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | 1 X X O . .
$$ | O X X O . .
$$ | X O O O O O
$$ | X X X X O .
$$ | . X . X O .
$$ | X X X X O .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | O 3 4 O . .
$$ | O 2 . O . .
$$ | X O O O O O
$$ | X X X X O .
$$ | . X . X O .
$$ | X X X X O .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | . 7 X O . .
$$ | 6 X 5 O . .
$$ | X O O O O O
$$ | X X X X O .
$$ | . X . X O .
$$ | X X X X O .[/go]
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | . O . O . .
$$ | X Y O O . .
$$ | X O O O O O
$$ | X X X X O .
$$ | C X C X O .
$$ | X X X X O .[/go]
+ + + + + + + + + +
Last but not least, "death" is lurking around the corner for groups that are
neither of type "2EL" nor of type "LIS".
Type 6:Black stones that are located inside an area that is surrounded by a white "2EL" group
(and which might contain further white "2EL" stones or groups") are said to be "dead stones".
- Click Here To Show Diagram Code
[go]$$W
$$ +-----------------
$$ | Z O . . O . O X .
$$ | . Z O O O O O X .
$$ | O O O X X X X X .
$$ | X X X X . . . . .
$$ | . . . . . . . . .[/go]
Type 7:All other black stones shall be "alive in seki".
- Click Here To Show Diagram Code
[go]$$W
$$ +-------------
$$ | . O O X . .
$$ | Y O O X . .
$$ | O X X X X X
$$ | O O O O X .
$$ | . O . O X .
$$ | O O O O X .[/go]
+ + + + + + + + + +
For scoring, "dead stones" are taken from the board and counted as prisoners for the opponent. "Territory" is the amount of unoccupied points that are surrounded by "2EL" groups.
No reference to "dame" is needed any longer.
However, it is absolutely necessary to check the exact formulation of the phrased rules (if anyone wanted to do so, based on the thoughts above) to undesirable side effects (e.g. the complex open ko shapes mentioned in the very beginning) !!!
_________________
The really most difficult Go problem ever:
https://igohatsuyoron120.de/index.htmIgo Hatsuyōron #120 (really solved by KataGo)