Fighting Ko and Disturbing Ko
"Fighting ko" and "disturbing ko" are ko types invented by Ing Chang-ki, ambiguously used in some versions of Ing rules. A formal definition of these two ko types is available in the paper by Robert Jasiek called Types of Basic Kos.
Official Definition from Ing Rules
From Ing's Wei-ch'i Rules:
"A fighting ko involves repetitive removal; immediate removal of hot stones is prohibited. A disturbing ko involves cyclic removal; the disturber is prohibited from recycling."
"When life and death are not settled, repeated fighting for breaths is called a fighting ko. The ko stones in the repeating fight are called hot stones. Hot stones cannot be removed until after an interval of one board play or pass play."
"When life and death are settled, recycling of interchangable breaths is called a disturbing ko. The player who starts a disturbing ko is called the disturber. By attacking his opponent or using a double ko, the disturber creates a disturbing ko with no hot stones. After one cycle, the disturber is never allowed to continue disturbing."
"Traditional rules had only single hot stones, which did not satisfy the requirements of fighting ko. The SST rules introduced double hot stones for use in the eternal life position and twin hot stones for use in triple ko, thereby resolving all fighting kos. The fighting ko rule is that hot stones cannot be removed until after an interval of one board play or pass play; this eliminates special rulings about fighting ko.
"A disturbing ko has no hot stones. Hot stones do not work in a disturbing ko because both sides can remove different stones; they do not have to fight over the removal of hot stones. A disturbing ko is initiated by one player, who is called the "disturber". His opponent is said to have been "disturbed." A disturbing ko only serves to exchange breathing points. It does not affect life and death but just prevents the game from ending."
See also: Ing ko rule
iopq: So, is this equivalent to a superko rule, but where one is allowed to return the position to the original state?
RobertJasiek: Of course not. That linked page does not explain Ing-ko but only pretends to do so. See my rules pages for explanations.
sigs: what do you mean by of course not? What is the practical difference? The position returns to where it was before taking in the first place, and the one who took the first stone in the cycle has to come up with something else. Still, it's more complicated than superko.
RobertJasiek: Commentary 1, Commentary 2, Examples 1, Examples 2
More on /Logical definition subpage.