jaeup wrote:
Bill Spight wrote:
==== Article 8. Territory
After all dead stones, if any, have been removed, empty points that are surrounded by stones of the same player are called eye points, and any empty points that are not eye points are called neutral points. All stones that surround the same eye points belong to the same group. A group is called a seki group if it is adjacent to a neutral point, or if one or more of its stones is in atari. Eye points that are surrounded by a group that is not a seki group are territory. Territory belongs to the player whose stones surround it.
I agree that after removing dead stones, defining seki is doable with simple words. However, in some cases, removing "dead stones" is not recommendable. (One example is a double ko seki. Another example is the case when someone forgot to capture dead stones inside a seki.)
My Japanese-style rules do not make use of hypothetical play, which assumes correct play. Instead, they use an operational definition of life and death, which depends upon the agreement of the players (which could be mistaken, OC) or upon the result of actual play in one or more encore rounds of play (which could include mistakes in the play). Here is the rule about ending play.
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Article 9.3. Ending the Game
If the players agree about dead stones at the end of a round of play, as provided in section 1, the game ends.
If a round of play ends in a position where a previous round ended, the game ends without agreement. All stones on the board are alive.
Since stones in double ko seki and the like are not dead by this definition, the definition of seki states:
A group is called a seki group if it is adjacent to a neutral point, or if one or more of its stones is in atari. If the game ends without agreement, all stones on the board are alive. If a player could have captured a stone but forgot to do so, tough luck.
BTW, during agreement, each player identifies only their own stones as dead. If their opponent thinks that they have left out a dead stone, play may resume and the opponent may try to capture it.
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When I tried my best to logically define seki stones leaving all dead stones on board, I came up with this sentence. (Assume live and dead stones are identified, and thus dames and eyes are also identified. Still, the task is not easy.)
The condition for a live Black stone to be a seki stone is as follows: Starting from the Black stone if a path to a dame exists only through i) "live Black stones" ii) "dead White stones each having a path to a Black eye only through dead White stones" and iii) "empty points".
Don't worry that you can't understand it in 5 minutes. Whenever I come to this part of my book, I check all sample figures I prepared three times to make sure that the definition works. (I tried to make it simpler, but anything less than this will create a non-intuitive counterexample.)
Defining life and death by agreement or actual play means that the definition is not ideal, but depends upon the actions of fallible humans. One may argue about whether a stone ought to be dead or alive, but operational definitions are scientifically impeccable.
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BTW, as was already discussed above, the original Japanese text only includes the words "stone", but while reading it, one feels that they implicitly assume the concept of "collection of stones" (which one may call a group) in a sense that all 20 Black "stones" of the above shape are collectively identified as seki stones.
OC,
ishi in Japanese can be singular or plural, and the Japanese rules do not include words like
string, chain, dragon or
group. To the extent to which that causes ambiguity or confusion, well, the Japanese can be inscrutable even to themselves.