An interesting new rule idea.

[Joelnelsonb]

An "independent group" is a group of connected stones, all sharing liberties which require two separate eyes in order to permanently maintain their place on the board. Compare this to a group left in seki which is not independent but depends and shares liberties with an enemy group. In Japan they call it seki, in America we call it a Mexican Standoff

[RobertJasiek]

for all practical purposes, to count the territory is the most convenient way to play go everyday

Then why does nobody "count the territory" but are there rulesets that count "territory plus opposing prisoners"? ;)

Convenient - no.

Rules are arbitrary. They don't need justification. Which ones are better is all a matter of taste, convenience, beauty etc.

Rules in general are not arbitrary, but there are explanations and justifications for them. For particular rules, there is a choice among equally valid alternatives; for every such choice, it is a matter of external requirements or, if none are presumed, personal preferance.

[tiger314]

An "independent group" is a group of connected stones, all sharing liberties which require two separate eyes in order to permanently maintain their place on the board. Compare this to a group left in seki which is not independent but depends and shares liberties with an enemy group. In Japan they call it seki, in America we call it a Mexican Standoff

May I ask you to identify individual groups and the final score in the following (made up) game:

(;GM[1]FF[4]CA[UTF-8]SZ[9]AB[ac][bb][bc][cb][ca][aa][gg][fh][fi][gi][hi][hh][ih][ig][if][hf][ii][ag][bg][bf][be][ae][ch][dh][dg][df][ci][ef][de][dd][ed][fd][fe][ec][eb]AW[ei][eh][eg][fg][ff][gf][ge][he][ie][ad][bd][cd][cc][dc][db][da][bh][ai][cg][cf][ce][fc][gc][gd][di][fb][fa][hc][gb][ic][hb][id][ea][ha][ia])

It would seem to me that under your definition the single stone in the top left corner is a group on it's own, since it is not connected to any other stones. Yet, I would usually consider it a part of the independently alive black group.

[Bill Spight]

I think that one of the main problems with group tax is defining what a group is. "A group" may seem like a simple concept, but it is actually quite hard to define it precisely. You might want to post a good definition of a group before going further with your group tax idea.

Well, a "group tax" is not a tax, maybe it does not apply to groups, either. Language is funny.

As for a precise definition, there is an operational definition by play. Play reaches a point where there is one or more one point eyes which, if and only if filling one of them allows the opponent to take the stones forming those eyes on the next move. The number of such eyes is the group tax for those stones.

You can also use hypothetical play, which is usually how the group tax is determined.

Edit: Oops! There are eyes that, if filled, do not allow the opponent to take on the next move, but the stones that formed that eye are still dead. That is the test, isn't it? Filling an eye kills your own stones.

[Bill Spight]

May I ask you to identify individual groups and the final score in the following (made up) game:

(;GM[1]FF[4]CA[UTF-8]SZ[9]AB[ac][bb][bc][cb][ca][aa][gg][fh][fi][gi][hi][hh][ih][ig][if][hf][ii][ag][bg][bf][be][ae][ch][dh][dg][df][ci][ef][de][dd][ed][fd][fe][ec][eb]AW[ei][eh][eg][fg][ff][gf][ge][he][ie][ad][bd][cd][cc][dc][db][da][bh][ai][cg][cf][ce][fc][gc][gd][di][fb][fa][hc][gb][ic][hb][id][ea][ha][ia])

It would seem to me that under your definition the single stone in the top left corner is a group on it's own, since it is not connected to any other stones. Yet, I would usually consider it a part of the independently alive black group.

Under any number of variants of No Pass Go the final net score is 1 point for White. Given the net score and the number of points of territory, you can figure out the group tax.

[Joelnelsonb]

May I ask you to identify individual groups and the final score in the following (made up) game:

(;GM[1]FF[4]CA[UTF-8]SZ[9]AB[ac][bb][bc][cb][ca][aa][gg][fh][fi][gi][hi][hh][ih][ig][if][hf][ii][ag][bg][bf][be][ae][ch][dh][dg][df][ci][ef][de][dd][ed][fd][fe][ec][eb]AW[ei][eh][eg][fg][ff][gf][ge][he][ie][ad][bd][cd][cc][dc][db][da][bh][ai][cg][cf][ce][fc][gc][gd][di][fb][fa][hc][gb][ic][hb][id][ea][ha][ia])

It would seem to me that under your definition the single stone in the top left corner is a group on it's own, since it is not connected to any other stones. Yet, I would usually consider it a part of the independently alive black group.

The score is white wins by 1 (given that both have 35 as is yet white can still fill in one more eye to get a 36th stone). That would of course be under strict stone scoring without any additional compensation points. It's a weird example, I admit. However, I would consider that stone in the top left to be sharing liberties with it's surrounding group given that its laying on the neutral fringe of the board (which in this case is treated like a wall of black stones). BUT, if you don't like that answer then that just means that we don't get to have a nice, pretty little concise statement to confine the group tax. You must simply say: A player must deduct one point for every necessary eye he has on the board (oh wait, that's also rather concise, isn't it...). Notice as in the example that white still has an unnecessary eye which is why he wins by my count. It's important to remember though that the idea of this thing were calling "group tax" is in no way a rule or even a subrule of the game. It's simply an aspect of the learning to count up the score without having to completely fill in the board as I did in the example I gave before. Compare this to life and death. No where in the rule book of Go should the terms "life and death" even show up. These are simply jargon that we use between players to describe a certain type of position. Instead of playing it out to completion, two skilled players can look and say "if we DID play this out, those stones would be captured without any chance of survival. Let's not waste our time. And for future reference, when we encounter stones like these, lets just call them "dead" so we both know what we mean. agreed?" The same is true for miai, seki, atari, along with kosumi, kakari, nobi and so forth. The point being that striving to write up a perfect definition that can be universally among players is a little pointless anyways. Just as long as were all on the same page and when the games over, we both know who won.

[Pio2001]

Compare this to life and death. No where in the rule book of Go should the terms "life and death" even show up.

This is true for stone or area scoring.
But territory scoring, as used in japanese rules, must rely on a strict definition of life and death. Under japanese rules, removing dead stones without paying the price of their capture is a right given by the rule. In area or stone scoring, it is a conventional practice not depending on the rule.

It is funny to think that a strict territory-minus-prisoner scoring would have nothing to do with the game of go as we know it, because every so-called "dead" stone would have to be actually captured for the eyespace to become one player's territory.
In fact, when we say territory-minus-prisoners, we actually mean territory-minus-prisoners-minus-dead-stones, where "dead" is supposed to be defined somewhere in the complete version of the rule.
Robert has found a very good definition of "life and death" : http://home.snafu.de/jasiek/sj.html

[RobertJasiek]

Robert Pauli suggested a predecessor of the definition.

[Bill Spight]

It's important to remember though that the idea of this thing were calling "group tax" is in no way a rule or even a subrule of the game. It's simply an aspect of the learning to count up the score without having to completely fill in the board as I did in the example I gave before.

Very important point. It underscores the fact that the so-called "group tax" logically depends upon the score, not the other way around. Yes, it is a shortcut to count the score, but unnecessary.

[hyperpape]

Rules are arbitrary. They don't need justification. Which ones are better is all a matter of [several forms of justification].

[tiger314]

The point being that striving to write up a perfect definition that can be universally among players is a little pointless anyways. Just as long as were all on the same page and when the games over, we both know who won.

The point is that there are games where big money is involved and "being on the same page" just isn't going to be enough. A well defined ruleset is necessary for a game where the outcome really counts. That being said, I see "A player must deduct one point for every necessary eye he has on the board" as a well defined rule which could be unambiguously applied (a definition of a "necessary eye" would be added, but that's a detail).

[RobertJasiek]

Defining "necessary eye" is possible for independent life via "two-eye-formation", "hypothetical-sequence", "hypothetical-strategy", "left-part", "compatible" and "force" and about as complicated as the Japanese 2003 Rules.
http://home.snafu.de/jasiek/j2003.html
Also note the existence of multiple threats, which require an abitrary choice in the definition. Compare
http://home.snafu.de/jasiek/wagcmod.html
http://home.snafu.de/jasiek/j1989c.html
Defining "necessary eye" for the strategic object "seki" (and not just for the fake-(in-)seki object of "being adjacent to / containing at least one dame") is an unsolved theoretical problem because the strategic object "seki" in general is still undefined.

EDITED