[Version 2; 2008-04-16; Robert Jasiek]
[Basic definitions are omitted.]
A move is either a play or a pass.
A move-sequence is a sequence of alternating moves.
Suicide is prohibited.
[Basic ko:] A play may not recreate the position just before the previous move.
The game consists of the following phases in order:
Optional: The dame and teire filling.
Optional: The analysis.
The game end removals.
Definition: The scoring.
Definition: The result.
Optionally resumption is possible after the alternation and until after the result.
The alternation is a move-sequence that starts by Black and ends by two successive passes.
Removed stones are added to the prisoners.
[Long cycle:] If an equal number of stones have been removed since just after a play created a position and until just after another play recreates the same position, the game ends as a tie. Tournament rules may specify a different result. In view of the difficulty to determine the first moment of such recreation, the players are not penalized for its delayed notice.
Informally the players may partially or completely fill what they consider dame and teire.
The final position is the position at the end of the alternation.
The analysis is applied to the final position.
The players may abbreviate the analysis wherever they agree.
Removed stones are not added to the prisoners.
A two-eye-formation is a set of one or several strings of the same player and exactly two empty intersections so that each of the strings is adjacent to each of the two intersections, none of the strings is adjacent to another empty intersection, and each of the two intersections is adjacent only to the strings.
A string is independently alive if each performed move-sequence transforms it into a two-eye-formation as follows. The string's player shall create a two-eye-formation while his opponent shall prevent that. The players perform as many move-sequences as they consider necessary. Each such move-sequence starts from the final position by the opponent and ends by three successive passes. The string and a two-eye-formation have at least one common intersection.
[Fixed ko:] A play is prohibited if the positions just before and just after it are the same and in the same order as the positions just before and just after an earlier play of the same move-sequence.
Each string of the final position is analysed to determine whether it is independently alive. One string after another is analysed for itself in some arbitrary order.
A region of one or several connected intersections is territory if it is adjacent only to one player's stones of one or several independently alive strings and does not contain any stone of the player or of an independently alive string of the opponent.
The players remove the stones from territory and add them to the prisoners.
If the analysis phase has been performed, then the territory is given and the removals are done accordingly.
If the analysis phase has not been performed, then territory is determined and removals are done informally due to the players' agreement.
The score is the sum of numbers of Black's territory intersections and prisoners of white colour minus the sum of White's territory intersections, prisoners of black colour, and the komi.
The counting calculates the score.
If the game is played in the real world, then Japanese fill-in counting is performed.
If the game is played in a virtual world, then the software performs the counting.
Black wins if the score is greater than zero.
White wins if the score is smaller than zero.
The game is a tie if the score is zero.
Resumption may be requested if one or both players do not agree to the dame and teire filling, the analysis, the game end removals, the scoring, the counting, or the result.
The alternation is resumed as if its last two passes had not occurred and the position and the numbers of prisoners are restored to the state of that moment.
If available, a referee may supervise analysis or resumption.
A referee may prescribe whether the analysis is performed hypothetically, on an extra board, or on the playing board. In case of the latter, the position is restored after each move-sequence.
Game procedure: One would like to separate rules of play from tournament rules. However, this is impractical for these rules because of the informality of the dame and teire filling, the optional analysis, the usage of resumption as a means to replace perfect play, etc.
Long cycle: If one player accumulates more prisoners during a repeated cycle, he might accumulate an excess of 361 prisoners and then pass; a rule for that is considered superfluous. It would be possible to use the Japanese 1989 Rules' rule but its "if the players agree" tells the reader nothing and its "without result" does not allow any strategic comparison to the results of scored games.
Dame and teire filling: Definitions would be tough and ugly, i.e., impractical. Informality is practical here. Omitting the phase with the consequence of alternate filling during the alternation would be possible but disliked by a great number of players using Japanese style rules. Filling during the alternation is also legal.
Life: The rules do not require an analysed string to remain on the board. It might or might not be captured during a move-sequence that shall transform it into a two-eye-formation. A transformation might consist just of passes if a string is already part of a two-eye-formation.
Life: Tradition of Japanese style rules demands life to be a rules concept. The majority of Western amateurs would prefer usage of pass stones and just one playout move-sequence. Such is out of the question for Japanese players. Therefore the remaining question is how to design life definitions for the traditional style. Under this presupposition, those used in the rules are as elegant as possible by reduction to the commonly known two-eye-formation. Furthermore, seki and no territory in seki are not introduced as exceptions in the rules because these concepts are not introduced at all while sekis are without territory nevertheless.
Life: Perfect play is not required. In practical application, perfect play would require an arbitrary number of move-sequences. Such would be impossible. Therefore the rules are more reasonable and allow the players to choose how many move-sequences they consider necessary. A supervising referee and the possibility of a resumption ensure approximation of perfect play nevertheless. Theoreticians interested in formal definitions of strategy and perfect play should use other rulesets instead.
Life: Although the rules do not speak of locality explicitly to avoid artificial concepts, they use some locality implicitly by analysing each string for itself and by requiring a common intersection of an analysed string and a two-eye-formation for it.
Three successive passes: A move-sequence during the analysis ends by three successive passes so that passes serve as ko threats and 1-eye-flaws can be removed even if tenukis are not available. Regardless of rarity, Japanese rules tradition considers this necessary.
Fixed ko: A different long cycle rule is needed together with three successive passes so that the tradition of double ko sekis remaining on the board in a scored game is maintained regardless of their rarity at the game end. Japanese rules tradition dislikes superko; so yet a different rule is needed. Nobody wants an artificial move type "ko-pass for a particular ko" (like in the Japanese 1989 Rules) or "ko-pass for all kos". Besides nobody wants infinite move-sequences. The fixed ko rule is a possible solution. Not even theoreticians could construct a long cycle ko fight under it yet. That regular long cycles would have led to a game end already during the alternation and that each string is analysed for itself during the analysis makes it even much more unlikely that long cycle ko fights could occur during the analysis.
Tradition: In practical application, the combination of pass and ko rules approaches 99.99% of the tradition. Where it might still disagree, tradition itself has not been precise enough. It would be impossible to approach tradition more closely with applicable rules. Traditional hardliners will see a superko rule in the fixed ko rule although it is none and use that as pretence for avoiding applicability of the rules, although they could not explain the difference to 100% themselves.
Death and seki: Definitions for dead and seki are superfluous for the rules' definitions of territory and stones to be removed. They could be explained in more detailed commentaries. One type of dead is for the strings in territory. Then there are regular sekis, capturable strings in or nearby sekis, and capturable strings in between independently alive stones of both players. If a player wants to make prisoners there, he needs to capture stones during the alternation.
If a software makes counting mistakes and outputs a result without still offering resumption, then this is the software's mistake - not one of the rules.
The clock runs only during the alternation or a resumed alternation.