Unlike
http://home.snafu.de/jasiek/j1989c.html, this is not a detailed commentary, and unlike
http://home.snafu.de/jasiek/j2003.html, this is not detailed and complete interpretation of the intention behind the rules of play. Rather the reading of the Japanese 1989 Rules below is kept simple in language and is simplifying but does not hide the essential problems. "User-friendly" is an euphemism though because Japanese rules are very difficult, J1989 are much more difficult than necessary for Japanese style rules and J1989 hide many necessary aspects behind omission in their text.
***
Basic Rules
- The usual fundamental rules apply.
- The game consists of the phases 1. Competition, 2. Analysis, 3. Scoring.
- The Competition is a sequence of alternating moves.
- A move is either a play or a pass.
- Two successive passes end each sequence of moves.
- Removed stones become prisoners.
- Suicide is prohibited.
- The basic ko rule prohibits a player to make a play just after which the position just before the preceding opposing play would be recreated.
Independently Alive
- The only considered type of life is being independently alive.
- The concept independently alive relies in two other concepts: force and two-eye-formation.
- "force" is a technical term used in the Japanese 2003 Rules. It can be understood also intuitively though: That a player forces something means that he can and does choose his moves well enough to always achieve it - regardless of how the opponent replies.
- A "two-eye-formation" consists of one or several strings of the same player and exactly two empty intersections so that these properties are fulfilled: 1) Each of the strings is adjacent to each of the two intersections. 2) None of the strings is adjacent to another empty intersection. 3) Each of the two intersections is adjacent only to the strings.
- A string is "independently alive" if its player moving second can force to get a two-eye-formation on at least one of its intesections.
Analysis
- The Analysis consists of these steps: 1. Determination of the independently alive strings. 2. Removal. 3. Determination of territory.
- Each string is analysed separately. It is determined whether or not it is independently alive.
- For analysis of each string, imagined move-sequences starting by the attacker are considered. The defender shall try to prove "independently alive" while the attacker shall try to prove "not independently alive". Until the truth has been revealed, yet more sequences must be considered.
- During the step Removal, one considers the connected regions that are adjacent only to one player's independently alive strings and that consist of intersections being empty or having opposing not independently alive strings on, which are removed.
- During the step Determination of territory, a player's territory consists of the intersections of connected empty regions adjacent only to his independently alive strings.
Scoring
- Territory Scoring applies according to the territory determined in the Analysis.
- The score is visualized by means of Japanese Fill-in Counting.
Long Cycle Repetition
- During Competition, a cycle ends the game exceptionally and immediately. It is, however, tolerated that the players notice occurrence of a cycle delayed.
- During Competition, a cycle with an equal number of new prisoners lets the game result be a tie. For traditional reasons, this is also called "No Result" or "Neither Victory Nor Defeat" and the players are perceived to agree on the fact that such a cycle has occurred.
- During Competition, a cycle with an unequal number of new prisoners lets the game result be a win for the player with the smaller number. For traditional reasons, it is tolerated though that the players perform the cycle up to ca., say, a thousand times because the player having collected enough prisoners can at some time depart, let the opponent control the entire board but still win by Scoring.
- During Analysis, every sequence of moves leading to a cycle is treated as if ending upon completion of its first cycle. No stone played during such a cycle is "independently alive" though. This is equivalent to the original rules' implicit assumption of infite recurrence of that cycle.
Analysis: Corrected or Simplified Aspects
- The "enable" concept in the original rules leads to mistaken scores of some positions. Therefore it is not used but replaced.
- A replacement for "enable" could use concepts of "capturable life" like in the Japanese 2003 Rules. This would be unnecessarily complicated though. The only advantage of this approach is to get a tool for distinguishing alive strings in "sekis" from "dead" strings. Japanese rules excempt sekis from having territory. For the purpose of applying rules and determining the winner, it is therefore superfluous to identify sekis at all. Since we do not study strategy, application of the rules can be simplified here.
- An equivalence is known between always using "capturable life" versus using it only for sekis. Hence a next replacement step can be made: For "independently alive", it suffices to consider its relation to the concept "two-eye-formation".
- Due to the simplifying replacement, artificial terms of or missing in the original rules like "eye-point" or "in-seki" need not be considered, either.
Ignored Rules and Rules Aspects
- Trivial, easily corrected flaws are ignored.
- All tournament rules, komi and resignation are ignored.
- All procedurally superfluous extra game ending rules are ignored.
- The hypothetical ko rule is ignored. Instead the basic ko rule applies also during the Analysis. A "triple ko with one eye and one external ko" becomes a precedent: The strings of the player having the "eye" are independently alive while the opposing strings are not independently alive. The combination of a "double ko death" and a "basic ko fight about whether to dissolve it like a teire" elsewhere on the board becomes a precedent: In the double ko death, the strings of the player having the "eye" are independently alive while the opposing strings are not independently alive. The ko stone in the basic ko is not independently alive.
EDIT 1: Add "independently alive" in territory.
EDIT 2: Replace "permanent" by "independently alive". In the precedents, "alive" is replaced by "independently alive" and "dead" by "not independently alive". Minor corrections.
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RobertJasiek
= independently alive (here: single stone has successor that can be connected to "independently alive"
= independently alive (here: single stone has NO successor that can be connected to "independently alive"
= not independently alive
= not independently alive
= "stable"
= "removable"
= "removable"
= independently alive