Ambiguous Article Regarding Which Stones are in Seki
In an earlier post regarding Compulsory Dame Filling to Prevent Technical Sekis , we discussed the consequences of this article 8 of the rules, which defines seki by the presence of dame:
However, note that the sentence “Stones which are alive but possess dame are said to be in seki.” is somewhat ambiguous as to what exactly is meant by “stones” (whether only a solidly connected chain, or possibly some larger strategic group) and “possess dame” (whether that only means a chain being directly adjacent to dame or some broader sense of possession).
We came across an actual situation in a game that both illustrates this ambiguity and where the outcome of the game hinges on the specific interpretation (i.e., it makes a one point difference that decides between B+0.5 and W+0.5). Here is the key position in the bottom-right of the game, where there are black and white stones in seki, due to the unfillable dame at Q1:
Under one reasonable seeming interpretation of Article 8 (in isolation), one could perhaps say that “stones” is meant to mean a solidly connect chain (e.g., Black has two separate chains in the bottom-right area, with one 6-stone chain around Q2, and the other 14-stone chain around S4) and that “possess dame” means for a chain to be directly adjacent to a dame point (i.e., only the 6-stone black is adjacent to the dame point at Q1). With this interpretation, the eye points at R3 and T1 would not count as territory, since the 6-stone Black chain and 5-stone White chain are in seki for being adjacent to Q1. However, one could argue that the 14-stone Black chain is not in seki, since it is not adjacent to (and hence does not “possess”) the dame point Q1, which would then allow one to count the eye point at S5 as territory.
However, despite the above interpretation seeming reasonable (and being relatively easier to clearly define), it is not the correct interpretation intended by the Japanese rules. In actuality, all 20 of the Black stones in that corner should be viewed as a group that collectively possess the dame at Q1, which invalidates both eye points R3 and S5 from being counted as territory.
This correct interpretation is not obvious from reading the main articles of the rules alone, however (as pointed out by Robert Jasiek in this LifeIn19x19 forum thread), this interpretation is implied by the commentary in Example 24 of the “Examples of Confirmation of Life and Death” addendum to the official Japanese rules. Further analysis of the Japanese rules to explain this in more formal detail can be found in Robert Jasiek’s extensive commentary on Japanese rules.