Life In 19x19

Indeed, it is an open question if "all possible examples" and "known examples" are the same set. It is not quite so tough because examples fall into shape classes, which fall into classes of same cyclic behaviours. Nevertheless, until all possible shape classes will be revealed, it is an ongoing research field with the possibility of a need for updating the ko definition.

Currently, for the first time in history, the current definition is more powerful than our shape knowledge. Prior to my definition, we had not understood the common aspects of all know shapes well, except in an informal sense of "for some unclear reason being worth fighting about avoiding repetition".

Without definition destinguishing ko examples from examples that are not ko is done by appoximative understanding of what is - currently or possibly later during a game - for some unclear reason being worth fighting about avoiding repetition. Such comes from imagining representative ko fights happening about the shapes assumed to be ko. If there are examples for such ko fights in certain conceivable positional contexts, we perceive the thing as a ko. So this is a sort of (still ambiguous) implicit definition.

EDITED

This thread seems to be about the interpretation of the English word "definition." Robert, since you've already compared your work to the general theory of relativity, why not call it a theory of ko, rather than a definition of ko?

Currently, the definition is the most important part of the theory. The theory can, in principle, be expanded by a complete classification of all shapes / positions / sequences and proving the sketched proposition. This is a research topic for the following decades or centuries to complete the theory of ko.

I remember seeing a shape where a group of five stones gets repeatedly captured.

All u talking about are issues of convention. There is no definition or well-define-ness in itself. You can agree to use those words loosely, strictly, with a teleologic purpose, .... All that matter is: 1) all know what is talked about and 2) the consequences are not absurd or contradictory (because that would render the definition either as false or as a false-maker).

My two cents....

Edit: Sorry, too much investment...gotta substract one cent, thx^^.

A ko is when you can take and take back forever.

What if the ko rule is simply "do not recreate a previous position"?

Does that really cause seemingly unjust outcomes?

tentano wrote:What if the ko rule is simply "do not recreate a previous position"?

Does that really cause seemingly unjust outcomes?

Playing on an actual board, the farther away you get from traditional ko to various types of superko and other repeating positions, the harder it is to remember when you are obligated to break the cycle and when you can play through it.

Sure, but how likely is it really that you become stuck in, say, a 30-move repeating cycle?

Most of the infinite loops I've seen were under 10 moves, with the vast majority being about a simple ko.

It doesn't seem like something that's realistically a factor for amateur play, and pros would most definitely notice.

Matti wrote:I remember seeing a shape where a group of five stones gets repeatedly captured.

Great. I hope you can recall and share it. Already your quadruple ko stones have been a tough exercise.

tentano wrote:What if the ko rule is simply "do not recreate a previous position"?

Apply the definition to detect any kos in a given situation.

RobertJasiek wrote:

Matti wrote:I remember seeing a shape where a group of five stones gets repeatedly captured.

Great. I hope you can recall and share it. Already your quadruple ko stones have been a tough exercise.

I think I have it in my bookshelf.

Matti

Case number 1:

Click Here To Show Diagram Code

[go]$$B 1.A simple ko situation
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . , . . . . |
$$ | X X X X . . . . . |
$$ | O O O X X . , . . |
$$ | . O . O X X . . . |
$$ | . O O . O X . . . |
$$ +-------------------+[/go]

Click Here To Show Diagram Code

[go]$$B 2.ko is taken
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . , . . . . |
$$ | X X X X . . . . . |
$$ | O O O X X . , . . |
$$ | . O . O X X . . . |
$$ | . O O 1 . X . . . |
$$ +-------------------+[/go]

Obviously, retaking now cannot happen under my rule, because an earlier position would be revisited.

Click Here To Show Diagram Code

[go]$$B 3.ko is retaken
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . 2 . . |
$$ | . . . . . . 3 . . |
$$ | . . . . , . . . . |
$$ | X X X X . . . . . |
$$ | O O O X X . , . . |
$$ | . O . O X X . . . |
$$ | . O O . 4 X . . . |
$$ +-------------------+[/go]

Playing some stones elsewhere allows it to be retaken, because this position is not the same as diagram 1.
That takes care of the simplest case.

Case number 2:

Click Here To Show Diagram Code

[go]$$B 4.seki
$$ +-------------------+
$$ | X O X . X . X . O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Click Here To Show Diagram Code

[go]$$B 5.
$$ +-------------------+
$$ | X O X . X . X 1 O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

this is just silly in real life, but we're in theory here.

Click Here To Show Diagram Code

[go]$$B 6.
$$ +-------------------+
$$ | X O X . X 2 a . O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Black cannot play at a, because that recreates diagram 4.

Click Here To Show Diagram Code

[go]$$B 7.
$$ +-------------------+
$$ | X O X . X 2 5 . O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . 3 4 . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Black can play 5, because diagram 4 is not recreated.

I explicitly refuse to consider including things like how many captures there are, whose turn it is or other game state data which you cannot see expressed on the board's intersections.
I think adding such details just makes my idea overcomplicated and unfit for purpose.

That also means there are no special cases which need special descriptions. I would like to see some complicated cases, where my idea actually affects the outcome.

Especially if the changed outcome is perceived as less fair somehow.

tentano, all fine and well, but what is the point of your discussion of positional superko here? Do you want to express any relation to the topic of this thread, or do you just share my preference for this rule when used as a rule in an ordinary ruleset?

Hm, I don't know what I initially intended, but it looks like we're purely in agreement about which rule is the best, then.

tentano wrote: Case number 2:

$$B 4.seki
$$ +-------------------+
$$ | X O X . X . X . O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$B 4.seki
$$ +-------------------+
$$ | X O X . X . X . O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

$$B 5.
$$ +-------------------+
$$ | X O X . X . X 1 O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$B 5.
$$ +-------------------+
$$ | X O X . X . X 1 O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

this is just silly in real life, but we're in theory here.

$$B 6.
$$ +-------------------+
$$ | X O X . X 2 a . O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$B 6.
$$ +-------------------+
$$ | X O X . X 2 a . O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . , . . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Black cannot play at a, because that recreates diagram 4.

$$B 7.
$$ +-------------------+
$$ | X O X . X 2 5 . O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . 3 4 . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$B 7.
$$ +-------------------+
$$ | X O X . X 2 5 . O |
$$ | X O X X X X O O . |
$$ | X O O O O O O O O |
$$ | X X X X X X X X X |
$$ | . . . . , . . . . |
$$ | . . . . . . . . . |
$$ | . . , . . . 3 4 . |
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Black can play 5, because diagram 4 is not recreated.

I explicitly refuse to consider including things like how many captures there are, whose turn it is or other game state data which you cannot see expressed on the board's intersections.
I think adding such details just makes my idea overcomplicated and unfit for purpose.

That also means there are no special cases which need special descriptions. I would like to see some complicated cases, where my idea actually affects the outcome.

Especially if the changed outcome is perceived as less fair somehow.

OK, let's continue your second example.

Click Here To Show Diagram Code

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

and indicate "ko" threat and reply.

= pass

Now White cannot capture, because that would recreate the position after in diagram B 7.

Many, if not most, go players regard that as a problem.