Seeing no other comments on the basic ideas behind my proposed new confirmation phase I worked on the wording itself (which is not an easy task )
I corrected a lot of mistakes and modified various wording for clarification purpose.
I added also a lot of comments to explain the ideas behind the proposal.
Here is the new text:

Confirmation phase:

Preliminary definitions:

A "two-eye-formation" is a set of one or several groups of stones of the same player and exactly two empty intersections so that:
1) each of the groups of stones is adjacent to each of the two empty intersections¹,
2) each of the two empty intersections is adjacent only to the groups of stones².

The "inside border" of an area is all the intersections in the area which are adjacent to an intersection not in the area

The "outside border" of an area is all the intersections not in the area which are adjacent to an intersection in the area

A group of stones of a player is "pass-alive" if it keeps its alive status even if the player continues to pass whenever the opponent makes plays.

An area is "controlled" by a player if:
1) in the inside border you can find only stones of the player³.
2) in the outside border you can find only stones of the opponent⁴.
3) the area can be entirely covered by a "two-eye formation" through an hypthetical play (see below) assuming the outside border being pass-alive⁵

A "player's territory" is all the intersections which are empty or occupied by an opponent stone, in a player's controlled area⁶.

Confirmation phase procedure:
1) One player claims she "controls" a given area. This player is called the "defender" and the other player is called the "attacker"⁷
2) If this area cannot be "controlled" because inside or outside border do not fulfill the corresponding conditions (see above) then the confirmation phase procedure return to 1) for another claim
3) Hypthetical plays take place : the objective of the defender is to build a "two-eye formation" covering all the potential "controlled" area⁸. The attacker's objective is the opposite
4) If the defender succeeds the territory associated to the "controlled" area is declared the "territory" of the defender
5) confirmation phase procedure return to 1) for another claim

Definition:
A position is said to be "critical" if this position is reached after an attacker's ko capture followed by a defender's pass⁹.

Hypothetical play:
At the beginning of an hypothetical play there are no ko ban
The hypothetical play begins always by an attacker's move (a play or a pass) and then each player makes moves alternatively¹⁰.
Normal play rule is used during hypothetical play except that all the "permanently prohibited ko" created (see below) have to be taken into account (the attacker is not allowed to capture a ko which have been "permanently prohibited")¹¹
Three successive passes end always an hypothetical play¹²

Procedure to create "permanently prohibited ko"¹³:
As soon as a "critical position" is reached the defender¹⁴ may (it is not mandatory) claim for creating a "permanently prohibited ko":
1) The defender proves that she can either reach her objective or reach "critical positions" an infinite number of times
2) The defender proves she is able to prevent the attacker to make an infinite number of passes
3) If the attacker agrees to point 1) and 2)¹⁵ then the hypothetical play continues up to the following "critical position"
4) As soon as a new critical position is reached a "permanently prohibited ko" is automatically created for the ko capture made by the attacker before the last pass
5) Then the hypothetical play continues taking into account the "permanently prohibited ko" created and the defender may later create another¹⁶ "permanently prohibited ko" using again the procedure above.

Comment 1: the idea is that each group of stones has (exactly) two liberties
Comment 2 : this point implies that the two empty intersections themselves cannot be adjacent
Comment 3 : the inside border might be empty if the concerned area is made of all the board. In that case the outside border will be also empty
Comment 4 : Because empty intersection are not allowed in the outside border, that means that all outside dame has been filled
Comment 5 : because the outside border is considered pass-alive you do not need to play a move on the board which is not on the potential controlled area. You can always replace this move by a pass (eventually allowing you to retake a local ko)
Comment 6 : territory and its inside border are just the common concepts used by the players during all the game. In this context, claiming for a given controlled area is only natural. This defintion shows that territory is closely related to two-eye-formation. As a consequence in a region where exists a commonly called "seki", no territory can exist and that explains that no point can be counted in a "seki".
Comment 7 : the defender try to defend her territory against the attacker who will play first
Comment 8 : looking for a "two eye formation" corresponds basically to the work already done during game to verify that the player has really some points in a territory (no seki). In practice the two eye formation will never really build because the players will agree to the result far before the theoritical end of the hypothetical play.
Comment 9 : in a "critical" position it is always defender to play
Comment 10 : an hypothetical play starts always by the attacker => if the defender missed a teire move (during normal play) then the defender will not be able to prove she as a territory => teire moves should be played during normal play
Comment 11 : this rule prevents the attacker to create a loop avoiding the defender to build her two-eye-formation
Comment 12 : because the hypothetical play is basically played under normal play three passes are necessary to allow each player to retake an unsettled ko. OC, as usual, agreement between players may also end an hypothetical play
Comment 13 : the "permanently prohibited ko" is the key point to handle potential loops. The idea is to recognize that some loops are advantageous to a player (the easiest example is the monshine life). J89 uses pass-for-ko for that purpose but unfortunately side effects can be observed. As soon as an advantgeous loop has been recognised then a "permanently prohibited ko" allows to break the loop.
Comment 14 : only the defender can claim for creating a "permanently prohibited ko". The attacker has no need to avoid the defender to play a loop because such loop means that the defender has not reached her objective of building effectively a two-eye formation
Comment 15 : if the two players do not agree on point 1) and 2) even by using an another board for analysis then the referee will decide
Comment 16 : as worded several "permanently prohibited ko" may exist at the same time. Further study may conclude that using only the last "permanently prohibited ko" created is enough.

J89's CURRENT L&D example 18:

Translation into English:
"In the corner, the seven Black stones are 'dead stones', the two White stones are 'alive stones'. The thirteen Black stones in the centre are also 'dead stones', due to the 'collapse of the seki'."

Despite trying very hard, I was UNABLE to achieve this "desired" result by applying "GT territory rules".

Gérard, probably you may be so very kind to show me how your rules work here successfully (with regard to Black's groups, to be clear; i.e. "the entire corner is White territory")...

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

The answer is quite simple Thomas, the position you propose is quite different from example 18.

Let's consider example 18:

Click Here To Show Diagram Code

[go]$$B
$$ +----------------------
$$ | . O . X O . O X X O .
$$ | O X X X O O X . X O .
$$ | . X O O O X . X X O .
$$ | X X O . O O X X O O .
$$ | O O O O O X O O O . .
$$ | X X X X X X . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

In "GT territory rule" white claims for controlling all the corner by the sequence:

Click Here To Show Diagram Code

[go]$$W pass
$$ +----------------------
$$ | 1 5 3 X O . O X X O .
$$ | O X X X O O X . X O .
$$ | 4 X O O O X . X X O .
$$ | X X O . O O X X O O .
$$ | O O O O O X O O O . .
$$ | X X X X X X . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

Click Here To Show Diagram Code

[go]$$W pass
$$ +----------------------
$$ | 6 O 9 X O 8 O X X O .
$$ | 7 X X X O O X . X O .
$$ | X X O O O X . X X O .
$$ | X X O . O O X X O O .
$$ | O O O O O X O O O . .
$$ | X X X X X X . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

with the result expected.

BTW J89 does not give the "good" result due to the now famous loop with the double ko and the pass-for-ko.

If you wish me to show you how "GT territory rule" handles your new (difficult!) position tell me and I will explain in detail.

I already did!!!

You might want to click at the hyperlink provided at the very start of my posting...

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

I think J89 revised the example exactly for this reason: the old version is buggy since the double ko is useless there regardless of rules.

The former version of this example had NOT been buggy at all, as the intended result can be reached without any difficulties.

But they must have revised the text of "Article 7, 7.2" BEFORE!!!

Otherwise, with the apparent initial version, the desired result would not have been achieved!
It is NOT the nested ko shape of Black's, but of White's, DOUBLE-ko group that matters. It would have been more than sufficient to just interchange the kind of DOUBLE-ko group.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

As I wrote this is exactly the problem. The result is the same regardless of rules, even just resumed playout with basic rules (since in that version the double ko doesn't even provide a single threat - ko pass abuse aside).


I doubt the text changed, current 7.2 still seem to match Davies translation as I quoted earlier.


The ko-pass abuse in double kos is a separate problem that affects several examples. But safe to assume that such is not allowed, one way or another.

(Even if the current text overlooks it, later they may fix that by requiring a normal pass of either player before passing for the same ko a second time, or whatever.)

It does NOT!

"それぞれ" (sorezore) is "each", "every", NOT "particular"!!!
And not only in Google Translate, but also in a "real world" paper dictionary.

Let me explain at bit deeper:
"木" (hon) is "tree".
"林" (hayashi) ==> More than only ONE tree ==> One tree and another tree and another tree ... ==> is "grove", "spinney", "small forest".
"森" (mori) ==> Many (/ a lot of) trees => is "wood", "forest".
(Japanese count multitudes "ichi, ni, takusan" => "one, two, many".)

"これ" (kore) is "this one here". I.e. "nearby" (the speaker).
"それ" (sore) is "that one there". I.e. "farther away" (from the speaker, maybe nearby the dialogue partner).
"あれ" (are) is "that one over there". I.e. "in a distance" (from both dialogue partners).

"それぞれ" (sorezore) is "それそれ" (soresore), with the second "そ" adjusted in the pronunciation, as it follows a vocal (e) in the compound.
==> More than only ONE of "that one there" ==> "that there" and another "that there" and another "that there" ... ==> "each", "every".

++++++++++++++++++++++++++++++++++++++++++++

By the way:
The adjustment of J89 must have happened BEFORE 2007.
I own a Japanese book, published in this year, that contains the CURRENT version of J89.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

Have you ever seen a Japanese text of 7.2 that was different from current one?

Dear jann,

I am afraid that we were disputing about nothing...

Cointidentially, I searched for older Japanese versions of J89 this morning, but failed to find any (there was always the modified L&D example 18 included). Either the memory of the internet does not go back far enough, or there had been no respective contents ever in the Nihon Kiin website. (Or I haven't looked long enough.)

After having failed with looking for the complete J89 text, I searched for pictures of the "critical" L&D examples that contained
-- either a double-ko with attached bent-four,
-- or a double-ko with attached moonshine-life.

After a while, while studying the relevant websites from which the pictures were taken, I noticed something.
-- Either the comments were a simple copy of the J89's comment (e.g. "In the corner, the seven Black stones ..."),
-- or they started with something like "(Admittedly) there is this double-ko on the right, BUT ..."

The "..." was always someting like "... Xxxxx's stones at the left ARE dead, so after the collaps of the (temporary) seki, ..."

That would confirm what you wrote about the traditional Japanese understanding of double-ko in such combined positions.
(Which, by the way, agrees with the result of my analyzes regarding the "INTENDED" result of the status comfirmations.)

It seems to me now that Japanese tradition examines the "attached" formation INDEPENDENTLY (that is my "There in no double-ko during status confirmation.")
This implies that Japanese tradition would NEVER use the double-ko captures as a part of a sequence that frustrates the capture of the attached part of the combined formation forever. This is what you called an "abuse" of the double-ko cycle (and matches with my "A capture into a double-ko must not be used as a ko-threat.")

The remaining problem seems to be (ONLY) that the authors of J89 (apparently) did NOT want this "traditional understanding" becoming an EXPLIXITE part of the rules.
But have come up with some kind of "replacement mechanism". Which, in the understanding of James Davies' translation of the (supposed) initial version of that "replacement mechanism" ALONE (i.e. WITHOUT any additional knowledge of that Japanese tradition) did not really work.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

Click Here To Show Diagram Code

[go]$$B
$$ +----------------------
$$ | . O . X O X O . . . .
$$ | O X X X O X O O . . .
$$ | . X O O O X X O O . .
$$ | X X O O . O X X O , .
$$ | O O O . O X . X O . .
$$ | X X O O X . X X O . .
$$ | . X X O O X X O O . .
$$ | . . X X X O O O . . .
$$ | . . . . . . . . . . .
$$ | . . . , . . . . . , .[/go]

This position is very interesting indeed and ask a lot of questions concerning the logic of japanese go.

I do not know what could be the expected result and I guess very few people can give this expected result.
When reading the exchanges between Thomas and Jann I discover that this position was the original position for example 18 but this position has been replaced by a simpler one. Why this replacement? Two possible answers
1) this position corresponds to a buggy analyse
2) No agreement for the expected result has been reached

I have not the answer but I perfectly know what guided me when building the "GT territory rule".
First of all I have been very influenced by Jann post https://lifein19x19.com/viewtopic.php?p=266694#p266694.
Unless you have a good reason to do differently you must trust "normal play" to decide the status of the different groups of stones.

In area oriented rules the things are simple : you use normal play till the end of the game.
In territory oriented rules it is not as simple : normal play stops after two passes but it is not the end of the game. The confirmation phase begins and the particularity of territory oriented rules is that normal play cannot simply be used in this confirmation phase.

My own analyse tells me that it exists only two cases in which other considerations are used instead of simple normal play.

1) The most important case is to recognise that regions on the board may be considered independant (remember how Thomas drawed separations on the board by means of two-eye alive groups). This point is absolutly crucial in the logic of territory rules. The two basic examples are the following:

Click Here To Show Diagram Code

[go]$$B
$$ +----------------------
$$ | . O . X O . . . . . .
$$ | O X X X O . . . . . .
$$ | . X O O O . . . . . .
$$ | X X O . . . . . . . .
$$ | O O O . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | X X X X X X X . . . .
$$ | O O O O O O X . . . .
$$ | . X X X . O X . . . .
$$ +----------------------[/go]

Click Here To Show Diagram Code

[go]$$B
$$ +----------------------
$$ | . X . X O . . . . . .
$$ | X X X O O . . . . . .
$$ | O O O O . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | X X X . . . . . . . .
$$ | O O X X X X . . . . .
$$ | . O O O O X . . . . .
$$ | O X O . O X . .
$$ | X X X O O X . . . .
$$ | . X . X O X . . . .
$$ +----------------------[/go]

This independancy is handled by J89 by the wording "enable". Yes OC "enable" is not well defined and it addresses basically you intuition as a go player. But you cannot ignore the idea of independancy.
Remember Jann's post https://lifein19x19.com/viewtopic.php?p=266962#p266962. "enable" only allows to resolve such positions, without the help of pass-for-ko.

2) the second case is to allow breaking loops. When using only normal play loops cannot be breaked because no superko is used. Pass-for-ko is the tool chosen by J89 to break these loops and this tool is quite efficient in examples 8, 16, 17, 18 (I do not consider example 11 which is reolved by "enable" tool).

In all other situations my view is to trust normal play for finding the status of the groups (see Jann post https://lifein19x19.com/viewtopic.php?p=266694#p266694 I mentionned above)

With this in mind I consider that the pass-for-ko may be used abusively, I mean in case with no loop where normal play can be used very easily.

Let's take an example to illustrate independancy:

Click Here To Show Diagram Code

[go]$$B
$$ +----------------------
$$ | . O . X W . . . . . .
$$ | O X X X W . . . . . .
$$ | . X W W W . . . . . .
$$ | X X W . . . . . . . .
$$ | W W W . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | X X X X X X X . . . .
$$ | O O O O O O X . . . .
$$ | . X X X . O X . . . .
$$ +----------------------[/go]

Is the upper left corner independant of the other parts of the board? As it is drawn it is not independant because the status of white marked stone is not clear.

Click Here To Show Diagram Code

[go]$$B
$$ +----------------------
$$ | . O . X W . W . W . .
$$ | O X X X W W W W W . .
$$ | . X W W W . . . . . .
$$ | X X W . . . . . . . .
$$ | W W W . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | X X X X X X X . . . .
$$ | O O O O O O X . . . .
$$ | . X X X . O X . . . .
$$ +----------------------[/go]

In this above position the upper left corner can really be considered independant.

Click Here To Show Diagram Code

[go]$$B
$$ +----------------------
$$ | . O . X W . O X . . .
$$ | O X X X W X O X . . .
$$ | . X W W W X O X . . .
$$ | X X W O . X O X . . .
$$ | W W W O O O O X . . .
$$ | X X X X X X X X . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ +----------------------[/go]

Clearly in this other position there are no independancy. The best proof of dependency is the following. Depending of the status of seven black stones in the corner, the three black stones at the top may be either dead or alive.

Now let's show you a new position in which the pass-for-ko is used (abusively) in a no loop situation:

Click Here To Show Diagram Code

[go]$$B
$$ +----------------------
$$ | . O . X W . O X . . .
$$ | O X X X W X O X . . .
$$ | . X W W W X O X . . .
$$ | X X W O . X O X . . .
$$ | W W W X O O O X . . .
$$ | X X X X X X X X . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$ +----------------------[/go]

Strict J89 application says that the two black groups are dead. Isn't it an unexpected result which goes against the go logic?

I'm not sure were are on the same page. I never talked about double ko abuse, only "pass-for-ko abuse" in double kos. By that I meant passing for a ko in a double ko (which forces the opponent to pass for the other to be safe), then take the ko (opponent answers), then pass for the other ko (forcing again, etc.) perpetually.

This is a longstanding question in J89 which has two possible answers:

1. Maybe passing for each ko is only required once for each player (see here)
2. Or the problem was overlooked by J89 authors, and will be fixed in the future (with some hack like requiring a normal pass of either player before passing for a ko a second time)

In both cases J89 tries to treat double ko sequences logically, by actual confirmation play, showing several examples and sequences with remote double kos. And - until anything supporting the opposite - I still think the Japanese text for 7.2 is still the same as what Davies (a bit freely) translated. My weak Japanese tells me it says something like "whichever ko recapture (he) passed for, THAT KO can be recaptured afterwards".

The one who can read is in advantage!

The position above IS the CURRENT L&D example 18, HAS BEEN L&D example 18 since at least 2007, and apparently replaced a former, and simpler, position that had been L&D example 18 at the time of James Davies' translation of J89 into English.

J89 has White's groups in the corner "alive", and Black's groups in the corner "dead".

Let me know if YOU are unable to reproduce this result using your GT territory rules. Then I can tell you the solution (returned from several walks with Honte until now ).

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

No the opposite. The simpler one was the original, which is defective since the double ko is useless even with just normal play.


+1 so far.


IMO the opposite again: "pass-for-ko" is the one that is supposed to create ko independence, "enable" is there to RECREATE some dependence (which is required by cases where capture is only possible at the cost of giving up something).


I think I see where the problem is in your logic. Remember I talked about some redundancy in your rules?

Essentially, you use two ideas: Korean-style localization, and a new rule vs moonshine loops. But the synergy is poor (or nonexistent) between these two, they are contradicting / redundant.

Korean localization (consider remote groups independently) is a historical answer for the moonshine problem. It is logically complete, and (even if not my preference) it works ok. The side effect of this approach is combined moonshine cases can live.

Japanese rules do NOT use such localization, J89 went for the approach of separating everything at the ko level instead (and consider global sequences, watching "enable"). This is another acceptable approach.

Now your rules: If you use Korean localization, why not accept combined moonshine? If you have a new, general rule for moonshine, why do you want Korean localization for? Without moonshine there is no good reason to consider L/D locally, normal play doesn't work like that. You can just use "enable" with your ko rule. OC, the result won't match J89 - but will be a logical consequence of having a (often better) territory ruleset that handles moonshine correctly without localization.

Your rules do not seem to give the expected (Japanese-like) result in the revised J89 example in question (bent4 + combined double ko) as that is a case where your two patches can not complement each other (like they do in combined moonshine cases).

Quite apparently, traditional Japanese understanding includes the general principle that there are NO ko-threats in a (temporary) seki during status confirmation.
Which also includes double-ko formations as a special case dealt with in Examples 16-18.

See L&D example 7-2: https://www.nihonkiin.or.jp/match/kiyaku/shikatsu-07-2.html

Please note that the comment declares White's seven stones in the bent-four as "dead" ONLY.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

Interesting Jann. It remains unclear for me if you consider that pass-for-ko may have bad effect in some situations like the following already identified. IOW are the results according to J89 text the expected results or are they unexpected results?
BTW, in the following example J89 and J2003 give the same results.

Click Here To Show Diagram Code

[go]$$B
$$ ----------------------
$$ | O . O . X . . O O . O
$$ | 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]

Click Here To Show Diagram Code

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

IMO these are unexpected side effects of the pass-for-ko idea (there were also a third one decades ago). Lightvector's example (the first above) is particularly bad - may or may not be considered borderline tolerable.

This also shows how dangerous it is to invent new rules for things that are not supposed to be there. If you change ko play OC many outcomes will change, and not always as desired. And again: there is no good reason for local views to begin with (besides moonshine) - normal play doesn't work like that.

OK, I will provide you with the "solution" earlier than intended, but which Gérard will not like at all, as it will be proven that GT City would have better opened its gates to dogs, especially Labradors like Honte with his "magical DOUBLE-ko spell".



++++++++++++++++++++++++++

Click Here To Show Diagram Code

[go]$$W
$$ +----------------------
$$ | . O . X O X O . . . .
$$ | O X X X O X O O . . .
$$ | . X O O O X X O O . .
$$ | X X O O . O X X O , .
$$ | O O O . O X . X O . .
$$ | X X O O X . X X O . .
$$ | . X X O O X X O O . .
$$ | X . X X X O O O . . .
$$ | X X X O O O . . . . .
$$ | O O O O . . . . . , .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

Black claims "controlled area" in the entire upper left corner.
Black is the "defender"; White is the "attacker", moving first.

Click Here To Show Diagram Code

[go]$$W pass
$$ +----------------------
$$ | 1 O . X O X O . . . .
$$ | O X X X O X O O . . .
$$ | . X O O O X X O O . .
$$ | X X O O 2 O X X O , .
$$ | O O O . O X . X O . .
$$ | X X O O X 3 X X O . .
$$ | . X X O O X X O O . .
$$ | X . X X X O O O . . .
$$ | X X X O O O . . . . .
$$ | O O O O . . . . . , .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

The defender's pass with creates a "critical position", as the attacker captured a ko with just before. Black claims for a "permanently prohibited ko", i.e. White's capture into the lower ko-shape of the double-ko is prohibited next time.

Please note that this will make the double-ko disappear AFTER the next ko-capture in it (Honte is lurking around the corner...).

Click Here To Show Diagram Code

[go]$$W
$$ +----------------------
$$ | O O 5 X O X O . . . .
$$ | O X X X O X O O . . .
$$ | 6 X O O O X X O O . .
$$ | X X O O X . X X O , .
$$ | O O O . O X . X O . .
$$ | X X O O . O X X O . .
$$ | . X X O O X X O O . .
$$ | X . X X X O O O . . .
$$ | X X X O O O . . . . .
$$ | O O O O . . . . . , .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

Click Here To Show Diagram Code

[go]$$W pass
$$ +----------------------
$$ | . 7 . X O X O . . . .
$$ | . X X X O X O O . . .
$$ | X X O O O X X O O . .
$$ | X X O O X 9 X X O , .
$$ | O O O . O X . X O . .
$$ | X X O O 8 O X X O . .
$$ | . X X O O X X O O . .
$$ | X . X X X O O O . . .
$$ | X X X O O O . . . . .
$$ | O O O O . . . . . , .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

The defender's pass with creates a "critical position", as the attacker captured a ko with just before. Claiming for a "permanently prohibited ko" is irrelevant here.

Click Here To Show Diagram Code

[go]$$Wm11 pass
$$ +----------------------
$$ | 2 O . X O X O . . . .
$$ | 1 X X X O X O O . . .
$$ | X X O O O X X O O . .
$$ | X X O O . O X X O , .
$$ | O O O . O X . X O . .
$$ | X X O O X x X X O . .
$$ | . X X O O X X O O . .
$$ | X . X X X O O O . . .
$$ | X X X O O O . . . . .
$$ | O O O O . . . . . , .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

gives atari in the corner.
Playing at , instead, will not lead to success either.

can only pass, as "x" is a "permanent prohibited ko" for her, as attacker.

Click Here To Show Diagram Code

[go]$$Wm11
$$ +----------------------
$$ | X O a X O X O . . . .
$$ | 5 X X X O X O O . . .
$$ | X X O O O X X O O . .
$$ | X X O O 4 O X X O , .
$$ | O O O 6 O X . X O . .
$$ | X X O O X x X X O . .
$$ | . X X O O X X O O . .
$$ | X . X X X O O O . . .
$$ | X X X O O O . . . . .
$$ | O O O O . . . . . , .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

captures into the double-ko here, also giving atari at White's group therein.
As a matter of course, he could also succeed by capturing at "a" in the corner first.

can only re-capture in the corner, as a move at "x" is prohibited for her.

captures White's double-ko group.

Click Here To Show Diagram Code

[go]$$Wm11
$$ +----------------------
$$ | . O . X . X O . . . .
$$ | O X X X . X O O . . .
$$ | X X . . . X X O O . .
$$ | X X . . . . X X O , .
$$ | . . . . . X . X O . .
$$ | X X . . X . X X O . .
$$ | . X X . . X X O O . .
$$ | X . X X X O O O . . .
$$ | X X X O O O . . . . .
$$ | O O O O . . . . . , .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .[/go]

The claimed "controlled area" is Black territory!!!
You will easily realise that this does NOT match J89's expectations!


++++++++++++++++++++++++++

What are the reasons for this striking result?

Well, you will have realised that the DEFENDER (sufficient liberties of their attachment to the double-ko provided) will be able to kill the attacker's double-ko group.
L&D Example 18 contains a sandwich with FOUR layers (i.e. even). The DEFENDER owns the OUTER double-ko shape (but which is the one expected to die).
The ATTACKER's layer at the other end of the sandwhich (here in the corner) is NOT CONNECTED to the OUTSIDE. This implies that BOTH layers of the ATTACKER will die in the process.


What is the difference to L&D Example 16 (double-ko with attached moonshine-life).

The attacker's double-ko group cannot be killed, due to the liberty-count of the attachment.
(In the case of nested ko-shapes for the inner double-ko group, the defender's double-ko group could survive. However, this would not help her, as she would be unable to find any suitable "controlled area".)
L&D Example 16 contains a sandwich with THREE layers (i.e. odd).
The DEFENDER's layer at the other end of the sandwich is CONNECTED to the OUTSIDE (i.e. Black's encirclement). The DEFENDER will be unable to prevent the ENTIRE attachment from becoming captured. Thus, there will be NO territory for the DEFENDER in any claimed "controlled area".
(This would be true even in the case she captured the attacker's double-ko group.)


++++++++++++++++++++++++++

By the way:
The same principle would apply here, in a corner position WITHOUT ko, which is probably easier to understand.

Click Here To Show Diagram Code

[go]$$B
$$ +----------------------
$$ | O . X O O O X X O . .
$$ | O O X O O . O X O . .
$$ | . . X O . O X X O . .
$$ | X X X O O X . X O , .
$$ | O O O O X . X X O . .
$$ | X X X O O X X O O . .
$$ | . X . X X O O O . . .
$$ | X X X X O O . . . . .
$$ | O O O O O . . . . . .
$$ | . . . , . . . . . , .
$$ | . . . . . . . . . . .[/go]

As a matter of course, White could also claim the corner being her "controlled area", and succeed.
White has 19 stones in the corner, Black has 18 stones. Thus, the corner is worth a surplus of two points of territory for Black.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

I agree with you Jann. Let me try a deeper analysis.
First of all you said in your previous post:
"pass-for-ko" is the one that is supposed to create ko independence, "enable" is there to RECREATE some dependence (which is required by cases where capture is only possible at the cost of giving up something).
That's a very good point Jann. We all know that any apparently independant regions may be linked by a ko fight. Using a pass-for-ko to avoid this influence between regions is good point. Agreed Jann.

What about the unexpected side effects of the pass-for-ko?

Click Here To Show Diagram Code

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

In normal play when Black takes the ko by , white find a local ko threat at , black should answer by and white is able to retake the ko at .
In confirmation phase it is not allowed to use a ko threat in order to retake a ko. Fine but the point is that the ko threat is here purely local (it is not a ko threat in completly different area on the board). Does that mean that local ko threat may be acceptable in a local ko fight?

Click Here To Show Diagram Code

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

In normal play Black takes the ko by one, white answers locally by and on white is able to retake the ko at
In confirmation phase it is not allowed to use a play on the board (to put a stone on the board) in order to retake a ko. Here again the point is that the move (here ) is purely local and we may wonder if it is acceptable that local move can be use in ko fight to retake a ko.

What is your view?

As I wrote earlier, I think you should think in terms of logical concepts.

For the Korean approach (regions considered separately), it is natural that local ko fights work the same way as in normal play (hence no problems here but there are combined moonshine cases).

For the Japanese approach these examples are again natural consequences. If ko fight is not allowed at all, even combined moonshine is dead, but that - in some rare cases - may also help the dying side. There is nothing wrong with that (1 pt diff for extra reinforcing move) - IF you believe the original theory/idea (absolute ko independence) was correct.

Which IMO is not really the case: there is nothing in go that suggests ko-independent L/D with no threats, no reason besides moonshine (and tradition afterwards). So this unnecessary difference to normal play shows me the Japanese concept itself is slightly (tolerably) wrong. Same with the Korean concept with bent4 + remote seki for example.

The reason to look at normal playout is both to stay close to Chinese/area, and also not to give any undeserved gifts to either player. You must have a tool for free captures from territory (for correct scoring), but there is no need for differences beyond the saved cost of pure cleanup moves. If you have a rule vs moonshine kos, "enable" without any locality seems the most correct.