You and I may agree to that, but the Nihon Kiin rules do not. If I get a pin in my hip, am I the same person? Philosophers disagree.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Why would white not be allowed to capture 1 on move 4? That stone (1) is not "hot" anymore, so it can be captured like in normal play. I'm probably a bit dense, but I really don't get how this is ambiguous or why it would require extra rules (or extra clarification of rules).

Consider this:

Click Here To Show Diagram Code

[go]$$Bc
$$ ----------------------
$$ | O O . X O . . . . . .
$$ | O X X X O . . . . . .
$$ | . X O O O . . . . . .
$$ | X X O . . . . . . . .
$$ | O O O . . . . . . . .
$$ | . . O O O O O O . . .
$$ | . O O X X X X O . . .
$$ | O O X X a O X O . . .
$$ | X X X . O . X O . . .
$$ | O O O O . X X O . . .
$$ | O O O O X X O O . . .
$$ | O O O O X O O . . . .
$$ | O O O O X O . . . . .
$$ ----------------------[/go]

Black has an enormous ko threat of playing "a", which would dissolve the seki in the lower left if white did not answer, and this ko threat costs black nothing. White has no way to eliminate this ko threat, if white plays then it will also dissolve the seki in the lower left in favor of black, due to shortage of liberties. So black has an unremovable ko threat here.

In the upper left corner, black is dead by bent-four-in-the-corner. Black is dead *even though* black has this enormous cost-free ko threat. And yet white also does NOT need to sacrifice the lower left seki either or ignore any black threats in order to be able to claim black as dead. And I think pretty much everyone agrees that this is the intent of the Japanese rules.

The way the Japanese rules appear to operationalize black being dead here despite having this massive ko threat is that after play stops, in the confirmation phase, a player is not allowed to recapture a ko even after playing ko threats. The only way to recapture a ko is to pass "for" that ko - i.e. to point at the ko, indicate an intent to be allowed to recapture in the future, and then pass the turn, giving the opponent a full free turn to do whatever needed to resolve that ko, if possible. If the opponent cannot or does not, *then* a recapture is allowed.

So what this operationally would look like is:

Click Here To Show Diagram Code

[go]$$Wc
$$ ----------------------
$$ | O O 1 X O . . . . . .
$$ | O X X X O . . . . . .
$$ | 2 X O O O . . . . . .
$$ | X X O . . . . . . . .
$$ | O O O . . . . . . . .
$$ | . . O O O O O O . . .
$$ | . O O X X X X O . . .
$$ | O O X X . O X O . . .
$$ | X X X . O . X O . . .
$$ | O O O O . X X O . . .
$$ | O O O O X X O O . . .
$$ | O O O O X O O . . . .
$$ | O O O O X O . . . . .
$$ ----------------------[/go]

And then:

Click Here To Show Diagram Code

[go]$$Wc
$$ ----------------------
$$ | 4 3 . X O . . . . . .
$$ | 5 X X X O . . . . . .
$$ | X X O O O . . . . . .
$$ | X X O . . . . . . . .
$$ | O O O . . . . . . . .
$$ | . . O O O O O O . . .
$$ | . O O X X X X O . . .
$$ | O O X X 6 O X O . . .
$$ | X X X . O 7 X O . . .
$$ | O O O O . X X O . . .
$$ | O O O O X X O O . . .
$$ | O O O O X O O . . . .
$$ | O O O O X O . . . . .
$$ ----------------------[/go]

And now at this point, despite , black is still not allowed to recapture the ko in the upper left. Black's only way to be allowed to recapture it is to pass a whole turn for it, where upon white would take that free turn to finish the situation and kill black.

Does that make it clear what the issue is here and why in the earlier example you asked about, white might also not be allowed to recapture?

Sorry, I didn't mean any offense. We agree the J89 rules are hopelessly ambiguous in several ways. Your formalization is one way to resolve those ambiguities. But the J89 rules being ambiguous almost by definition means that there is more than distinct way to resolve those ambiguities, and it was not obvious to me that logical ways you ended up resolving them would necessarily be the same way that Japanese players would resolve them or want to resolve them if they came up in an actual game.

J89 ambiguity, in any case, obviously makes it hard to know how to proceed.

Yes, it is difficult to perceive and so is not obvious that J2003 produces for all examples considered by Japanese pro players their preferred results and does not produce counter-examples for that purpose. J2003 does, however, not provide a procedure preferred by them, e.g., because they were not even aware of (hypothetical-)strategy as a concept that can be formalised and its application complexity, and the J1989 (and Korean rules) authors overlooked the necessity for local-2 and capturable-2 to map all two-eye-alive groups to the concepts of (un)capturability.

From my understanding, the confirmation phase determines the status of groups separately. So when determining the status of the upper left, the status of the lower left is irrelevant and on move 7 white can just ignore and capture at C13, confirming that black is dead in the upper left.

Then we rollback everything to determine the status of the lower left and that will turn out to be a seki.

So AFAIK if white responds at F5 on move , it would be a mistake, because there is no ban for black to recapture at A13 on move 8. If white plays correctly in the confirmation phase, the position should not reach the point where black can recapture, because white will resolve the issue on move 7.

So this position is not ambiguous under Japanese rules. Perhaps the rules aren't stated as clearly as they could, but this is how the confirmation procedure should turn out and black's bent four group is just dead. Please correct me if I'm wrong.

AFAIK it is the Korean rules that work this way (and maybe pre-89 Japanese from where those presumably originated). J89 does have global play in confirmation and the pass-for-ko rule, and this position is a legitimate anomaly for that rule.

Ok, so the J89 rules are inconsistent with actual practise before and after 1989. I know that Robert and Bill spent a lot of effort to fix inconsistencies in the J89 rules and now I'm beginning to understand why. Perhaps the Japanese chose to ignore these issues, because in practise they don't bother to follow the J89 rules to the letter anyway.

Did the Koreans ever write down the rules they use, or do they just refer to the J89 rules?

There are some written versions, rather skimpy though, unfortunately.

They ignored these issues because they did not study rules, their theory and consequences for examples carefully enough. The authors Sakai Takeshi, Saijo Masataka and maybe a few others tried hard but, by a factor 10+, not hard enough. I met both and it became clear that they overlooked everything I (and partly others) had discovered. Sakai's capturability approach for J89 (and later adopted for some versions of Korean rules) was a theoretically cute (but practically stupid) alternative approach to the (if understood simpler and more commonly known) concept of two eyes, was necessary at that time because of the then still existing knowledge gap of what might be a definition of life due to two eyes (the failures of, sic, J49 and WAGC Rules looming), but overlooked capturable-2 etc.

IIUC, the J89 rules have global play, but they consider the status of each group or stone separately, if the players do not agree about it. Since the play is hypothetical, there is nothing to roll back. As each group or stone is considered, the hypothetical play starts afresh.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Even though L/D is considered separately, the attacker cannot ignore threats elsewhere because of the "enabling" clause.

BTW, this is against the current consensus OC, but I think bent4 dead even with unramovable threats is a poor result. It is inconsistent with three points without capturing: the latter shows that the spirit of current rules is that "problematic" captures need to be played out (losing points in the process). But then again, in that case there is no real alternative.

I doubt if that is against the current consensus. Everybody who likes the J89 rules, raise your hand.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

I think the rulemakers of the J89 rule did a great job. At least I tip my hat to them.
However, it is also true that J89 rule is badly flawed as R. Jasiek keeps saying when he has a chance.
I know they had "global play" in their mind when writing the rule, but I strongly believe that only local plays must be allowed for the rule to have any hope to become logical.



In case you are trying to ask "Shouldn't every anti-seki result in both palyer's loss?", I think https://lifein19x19.com/viewtopic.php?p=252059#p252059 answers that there are potential anti-seki cases that both players do not mind asking resumption of the game, but the opponents still do not want to make further play.

_________________
Jaeup Kim
Professor in Physics, Ulsan National Institute of Science and Technology, Korea
Author of the Book "Understanding the Rules of Baduk", available at https://home.unist.ac.kr/professor/jukim/bbs/board.php?bo_table=notice&wr_id=5

This board position is still kicking around and is being discussed at the OGS forums. The main question is whether White owes teire -- a move to solidify the position (e.g., at 'a'). Since this post is old I'll try to give a recap and present the positions, and explain my position. And then I'll explain what the real problem is -- this position is not a proper end-of-game board state. Black would take the ko, force White to throw in, and then force White teire. White teire is required.

Click Here To Show Diagram Code

[go]$$
$$ ----------------------
$$ | O . O . X a . . O . O
$$ | O O O X Q X O O O O O
$$ | X X X O . O O . O . .
$$ | X . X O O O O O . . .
$$ | . X X . . . . . . . .
$$ | X X . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

Recap:
There's the question of whether White is alive, and whether the stones are seki, and the main question of whether White owes teire ('a', etc). No doubt the 3 Black stones are dead. And no doubt the 5 White stones can be captured but only if White gets to place stones such that the marked stone is no longer in ko (e.g., when there is a White stone at 'a').

Some people think that because the 3 Black stones are dead and the 22 White stones are alive, then then White is alive with territory and may take the 3 Black stones off the board.

Other people think that because the 5 White stones can be captured, that White owes teire. Otherwise the White stones will have dame and be seki without territory.

----------

My position:
I think that the 22 White stones are alive but that the 5 White stones are dead when considered separately. The intersection in the 5 White stones is dame, so those stones are seki stones, and the intersection of the 5 White stones is not territory. White owes teire.

Examples 24 and 25 show how stones are considered both as a whole and separately.


Here, is dead when considered separately (even though and the White stones as a whole are alive) and so point 'b' is dame:
白△は「死に石」白□は「活き石」である。したがって、ｂは「駄目」、ｃは目となる。


Here, the White and Black stones as a whole cannot be captured, but the single ko stones are dead and so points 'a' and 'b' are dame.

--------------------

I admit that the position is confusing. First, this position is not similar to any examples in the Japanese Rules because White's 17 stones are already alive and uncapturable and it is clear that the 3 Black stones are dead. There is nothing to "confirm" about the 17 White stones in L&D confirmation. Second, the positions in the Japanese Rules dealing with teire involve seki stones or dead stones on both sides (both situations without territory), not one side alive while the other is dead as is the case here.

Thinking about this more, I believe that the position is confusing because it is not actually a "proper" end-of-game position. I mean that additional moves would/should take place during actual game play. Specifically, Black would capture and force White to throw in, which would eventually result in White teire. So yes, White teire is required.

Backing up, the premise is that White is winning by half a point and that teire inside his territory would lose the game. So Black must force White teire. During the game (not so-called "hypothetical play"), Black would take the ko and cause White to throw in. If there is a Double Ko on the board, then White may not want to throw-in, play the Double Ko instead, and so this position may repeat and lead to No Result.

Click Here To Show Diagram Code

[go]$$
$$ ----------------------
$$ | O . O . X 2 3 . O . O|-| O . O . X . X . O . O
$$ | O O O X O X O O O O O|-| O O O X . X O O O O O
$$ | X X X O 1 O O . O . .|-| X X X O X O O . O . .
$$ | X . X O O O O O . . .|-| X . X O O O O O . . .
$$ | . X X . . . . . . . .|-| . X X . . . . . . . .
$$ | X X . . . . . . . . .|-| X X . . . . . . . . .
$$ | . . . . . . . . . . .|-| . . . . . . . . . . .
$$ | . . . . . . . . . . .|-| . . . . . . . . . . .[/go]

After White throws in and black captures, White is winning. But White cannot just pass in this position because Black will capture the White stones. So, White must capture the ko back. White is still winning but White cannot pretend that this position is acceptable to pass because Black will just retake the ko and threaten capture the 5 White stones. White must play teire and lose a point.

I agree with you, white must play teire in your example.
But what is your position for the following position, with the added?

Click Here To Show Diagram Code

[go]$$
$$ ----------------------
$$ | O . O . X . . Q O . O
$$ | O O O X O X O O O O O
$$ | X X X O . O O . O . .
$$ | X . X O O O O O . . .
$$ | . X X . . . . . . . .
$$ | X X . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

If the L&D status of the White stones were confirmed after the game is stopped:

Click Here To Show Diagram Code

[go]$$ pass, above 1, at 2
$$ ----------------------
$$ | O 7 O 5 X 2 3 Q O . O-. X . X X W . @ @ . @
$$ | O O O X O X O O O O O-. . . X P . @ @ @ @ @
$$ | X X X O 1 O O . O . .-X X X @ . @ @ . @ . .
$$ | X . X O O O O O . . .-X . X @ @ @ @ @ . . .
$$ | . X X . . . . . . . .-. X X . . . . . . . .
$$ | X X . . . . . . . . .-X X . . . . . . . . .
$$ | . . . . . . . . . . .-. . . . . . . . . . .
$$ | . . . . . . . . . . .-. . . . . . . . . . .[/go]

The 5 White stones are dead and their empty intersection is dame, not territory. This is because the L&D status of stones is considered as a whole and separately. As a whole with the other stones, 5 the White stones are alive. But separately, they are dead. The original 18 White stones (marked and , I apologize for marking the wrong diagram but I can't be bothered to change it now) are easily deemed separately alive in the original position. The original 23 White stones as a whole can also be confirmed to be alive because they cannot be captured as a whole. It doesn't matter whether 5 stones can be captured and 2 new stones cannot be captured because 17 of the original stones (having 2 eyes) cannot be captured at all.

The important thing to note is that the L&S status of the original 18 stones is not dependent on the L&D status of the 5 White stones -- the 18 stones are already deemed alive. There is nothing left to "confirm". My understanding is that new uncapturable stones and only re-confirm the status of the 18 White stones separately and the 23 White stones as a whole, but say nothing about the separate L&D status of the 5 White stones.

In situations where the L&D status is independent, I think that adding new uncapturable stones to already independently alive stones "confirms" nothing. Consider this example modified from the same diagram in the Japanese Rules:



For example, if passes for the Double Ko (instead of passing for the Upper ko as in the actual Example) then some might think that also needs to pass for the Double Ko, causing a never-ending passes and retakes in the Double Ko without ever resolving the upper corner. However, consider if passes for the Double Ko and captures White in the upper corner. This lets retake the Double Ko leading to capture of Black in the lower corner. Even in this case, the fact that White was able to create new uncapturable stones in the lower left corner says NOTHING about the L&D status of the White stones in the upper left because the stones in the lower left were already deemed to be alive by virtue of the double ko.

I think the same reasoning applies here because the 17/18 White stones are already deemed to be alive and new uncapturable stones at and "confirm" nothing about the status of the 5 White stones when they are considered separately. "Confirmation" is determining the status of something unknown. There is nothing unknown about the status of the 18 stones. Therefore, the possibility of playing new stones and has no bearing on L&D "confirmation."

So the 5 White stones are dead and their empty intersection is dame, not territory.

----------

I am considering if Black tries to force White teire. At first I thought Black could, but now I see that Black cannot. If black takes the ko:

Click Here To Show Diagram Code

[go]$$
$$ ----------------------
$$ | O . O . X 2 3 Q O . O- O . O . X . X Q O . O- O . O . X 2 . Q O . O
$$ | O O O X 4 X O O O O O- O O O X O X O O O O O- O O O X . X O O O O O
$$ | X X X O 1 O O . O . .- X X X O 1 O O . O . .- X X X O 1 O O . O . .
$$ | X . X O O O O O . . .- X . X O O O O O . . .- X . X O O O O O . . .
$$ | . X X . . . . . . . .-. X X . . . . . . . .-. X X . . . . . . . .
$$ | X X . . . . . . . . .- X X . . . . . . . . .- X X . . . . . . . . .
$$ | . . . . . . . . . . .- . . . . . . . . . . .- . . . . . . . . . . .[/go]

After White's throw-in, Black can retake the ko to threaten the 5 White stones, but because of White can also retake a ko, so Black cannot capture. After the throw-in during the game, Black cannot capture the 5 White stones in L&D confirmation, but could have captured before the game-play throw-in. Black should not throw-in because otherwise White would have dame in L&D confirmation and lose territory.

In the following:

Click Here To Show Diagram Code

[go]$$
$$ ----------------------
$$ | O . O . X b . O O . O
$$ | O O O X O X O O O O O
$$ | X X X O a O O . O . .
$$ | X . X O O O O O . . .
$$ | . X X . . . . . . . .
$$ | X X . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

If black captures at 'a', White will throw in at 'b', so that Black is dead in double ko. Black thus has no move here. On the other hand, White can capture at any time. So the black three stones are dead and all white stones alive. No stone needs to be added.

I think that this is not even a grey area, and that any ruleset or interpretation thereof that disagrees with this outcome is wrong.

_________________
A good system naturally covers all corner cases without further effort.

This is why Black will not capture and induce White to throw-in. And I agree that no stones need to be added because adding a stone does not change the life and death status nor does it change the amount of territory.

However, the intersection with the 5 White stones is still dame, not territory. The premise of this discussion seems to be whether White must play teire and win by half a point. But actually, because there is dame, teire does not lose a point. The points are the same. It's just that White has one less point than they thought. White loses either way.

----------

Example 24:

Even if Black cannot actually capture in the game and can always be replayed (double ko, etc.), and even if the 13 White stones including are living stones, when considered separately by itself is a dead stone and point 'b' is dame. Whereas is alive when considered separately.

----------

The 5 White stones are dead when considered separately.

Is this not consistent with how L&D status works in the Japanese Rules? Stones cannot rely on ko-threats to prove life. Here the ko threat is local, but still.

If the white stones are alive and the black stones dead, then there are no dame. There is no way for Black to capture the white stones, so they are alive. White can capture the black stones anytime, so they are dead. There are no dame.

_________________
A good system naturally covers all corner cases without further effort.