would PGN need updates following recent rule changes?

[MikeB]

Your answer is legitimate, if nothing else because I believe FIDE will likely reverse their decision, but asking the question seems also legitimate.

I hope they'll reverse it, because it's a terrible rule change.

We truly live in interesting times, if they don't reverse it, it could be the end of chess as we know it.

My understanding is that illegal moves are still considered illegal, and can be penalized, but only if a claim is made before other moves are made, otherwise the illegality 'stands'. A potential problem is that it may encourage such illegal moves in losing positions, with the hope that the opponent may not notice it.

One possible “outside of the box” solution - play all rapid and blitz games online where the client software would not accept any illegal moves or possible enhance the dgt boards to flag any illegal moves. Illegal moves , imho, should not be allowed and should be penalize. The new rules are rediculous and the pgn standard already has a protocol for this and there is no need for an update. Just my $.02

[hgm]

If the position after the illegal move is illegal you can record the remaining game as comment inside {}. Nothing have to be changed in PGN spec. IMO.

I don't consider that a desirable / acceptable solution. If FIDE rules allow continuation of a game after a 'FIDE-illegal' move (a more accurate term would be 'illegalisable move'), then it should be possible to record the entire game in a homogeneousway. IMO the existing PGN spec aleady allows that, because it does not contain an explicit clause to alter the meaning of 'illegal' from the normal one. Insisting that redefinition of 'illegal' in the FIDE rules would alter the meaning of the PGN standard from what it was, would IMO indeed require a change of the wording of the PGN standard (avoiding the now tainted word 'illegal') to preserve the old meaning.

[casaschi]

If FIDE rules allow continuation of a game after a 'FIDE-illegal' move (a more accurate term would be 'illegalisable move'), then it should be possible to record the entire game in a homogeneousway.

That's sort of the aim of my original post, to assess wheter it's worth to properly record a game compliant to the new FIDE rules and only then how to actually doit with reasonable effort.

IMO the existing PGN spec aleady allows that

This is where I do not follow you anymore.

You suggest in an earlier post that my quirky illegalisable move could be coded in PGN as f7g4,@@h4,Ng3g2, but in the PGN standard of Steven Edwards that notation is nowhere described or even suggested: it does not describe how to combine more move-components into a single move (allthough a comma seems reasonable), it does not describe how to describe dropping a piece in/out of the board (allthough @ is in use to describe bughouse games) and so on. More important, it does not list all the options and possibilities taken into account.

There's a fundamental difference between assuming some current practice as the obvious extension to a standard to fulfill a new requirement and actually extending the standard to cover the new requirement in an universally agreed and comprehensive way. Example: the PGN standard defines a number of NAG codes (numeric coding of standardized comments); unfortunately the definition omitted a few commonly used comment strings (like some of the chess informant symbols such as the ones for "novelty", "better is" or "with the idea"), resulting in different competing proposals (usually from different programmers of chess software) to fill the gap. Often different competing proposals result in incompatible software writing/reading incompatible data. Exactly what the PGN standard is there to avoid.

So, if you want the PGN standard to include those illegalisable moves, it seems to me the PGN standard needs to be extended.

An alternative however could be to keep the PGN standard exactly as it is today (without support for illegalisable moves) and split any game containing illegalisable moves into a sequence of game fragments, each fragment consisting only of sequences of legal moves. The illegalisable moves would be missing, of course and at the fragment boundaries there would be a jump from a legal position to the next legal position after the illegalisable moves: some information would be lost (bad) but you'd avoid the headache of coding any possible combinations of illegal things that could turn into an illegalisable move. Not perfect but very pragmatic. It would help though if this way to deal with illegal moves was agreed as well, but a short appendix to the standard would do.

[gbtami]

If FIDE rules allow continuation of a game after a 'FIDE-illegal' move (a more accurate term would be 'illegalisable move'), then it should be possible to record the entire game in a homogeneousway.

That's sort of the aim of my original post, to assess wheter it's worth to properly record a game compliant to the new FIDE rules and only then how to actually doit with reasonable effort.

IMO the existing PGN spec aleady allows that

This is where I do not follow you anymore.

You suggest in an earlier post that my quirky illegalisable move could be coded in PGN as f7g4,@@h4,Ng3g2, but in the PGN standard of Steven Edwards that notation is nowhere described or even suggested: it does not describe how to combine more move-components into a single move (allthough a comma seems reasonable), it does not describe how to describe dropping a piece in/out of the board (allthough @ is in use to describe bughouse games) and so on. More important, it does not list all the options and possibilities taken into account.

There's a fundamental difference between assuming some current practice as the obvious extension to a standard to fulfill a new requirement and actually extending the standard to cover the new requirement in an universally agreed and comprehensive way. Example: the PGN standard defines a number of NAG codes (numeric coding of standardized comments); unfortunately the definition omitted a few commonly used comment strings (like some of the chess informant symbols such as the ones for "novelty", "better is" or "with the idea"), resulting in different competing proposals (usually from different programmers of chess software) to fill the gap. Often different competing proposals result in incompatible software writing/reading incompatible data. Exactly what the PGN standard is there to avoid.

So, if you want the PGN standard to include those illegalisable moves, it seems to me the PGN standard needs to be extended.

An alternative however could be to keep the PGN standard exactly as it is today (without support for illegalisable moves) and split any game containing illegalisable moves into a sequence of game fragments, each fragment consisting only of sequences of legal moves. The illegalisable moves would be missing, of course and at the fragment boundaries there would be a jump from a legal position to the next legal position after the illegalisable moves: some information would be lost (bad) but you'd avoid the headache of coding any possible combinations of illegal things that could turn into an illegalisable move. Not perfect but very pragmatic. It would help though if this way to deal with illegal moves was agreed as well, but a short appendix to the standard would do.

Seems this is the current practice as you can see in twic or in Ed's new millbase .pgn
Here is an example from mb-2017.pgn

[Site "Bad Wiessee GER"]
[Date "2016.11.04"]
[Round "1"]
[White "Kozul, Z"]
[Black "Kveinys, A"]
[Result "1/2-1/2"]
[WhiteElo "2619"]
[BlackElo "2509"]

1.d4 d5 2.c4 c6 3.e3 Nf6 4.Nc3 a6 5.Nf3 Bf5 6.Qb3 Ra7 7.a4 e6 8.a5 h6 9.
Qb6 Qxb6 10.axb6 Ra8 11.c5 Nbd7 12.b4 {now the illegal 12... O-O-O was
played} 1/2-1/2

[Event "20th OIBM 2016"]
[Site "Bad Wiessee GER"]
[Date "2016.11.04"]
[Round "1"]
[White "Kozul, Z"]
[Black "Kveinys, A"]
[Result "1/2-1/2"]
[WhiteElo "2619"]
[BlackElo "2509"]
[FEN "r3kb1r/1p1n1pp1/pPp1pn1p/2Pp1b2/1P1P4/2N1PN2/5PPP/R1B1KB1R b KQkq - 0 1"]

1...O-O-O 2.Bb2 Ne4 3.Nxe4 Bxe4 4.Nd2 Bc2 5.Be2 g5 6.e4 Bg7 7.f3 Nb8 8.O-O
dxe4 9.fxe4 Bxd4+ 10.Bxd4 Rxd4 11.Nc4 f5 12.exf5 exf5 13.Rac1 Be4 14.Rcd1
Rhd8 15.Rxd4 Rxd4 16.Nd6+ Kd7 17.Nxe4 Rxe4 18.Bd3 Rxb4 19.Bxf5+ Ke7 20.
Re1+ Kf7 21.Be6+ Kf8 22.Bc8 Rc4 23.Bxb7 Rxc5 24.Bxa6 Nxa6 25.Ra1 Rb5 26.
Rxa6 Ke7 27.Ra7+ Kd6 28.Rh7 Rxb6 29.Rxh6+ Ke5 30.Kf2 Kf5 1/2-1/2

Just notice that this happened way before 2018.01.01

[syzygy]

Because both under old A4.2 both under new A4.2 "illegal move shall stand" can happen, this is not a new problem at all.

Until now "illegal move shall stand" only occurred as a mistake with disregard of the games rules.
With the new FIDE rules, "illegal move shall stand" can happen by a conscious decision of a player in full compliance with the rules.

This seems a major difference to me; if FIDE explicitly allows for this event to happen then it's legitimate to ask the question whether the event should be coded and recorded accordingly in the chess notation.

But does it really matter whether the players were or became aware of the illegal move? The fact of the matter seems to be that games with illegal moves have been produced in the past and will be produced in the future, at least in OTB chess. It seems unlikely that under the new rules there will be many more games with illegal moves than under the old rules (perhaps their number will double or even triple, but it will remain very small compared to the total number of games played).

According to Article 7.5.1 of the Laws of Chess in force until 31 December 2017:

An illegal move is completed once the player has pressed his clock. If during a game it is found that an illegal move has been completed, the position immediately before the irregularity shall be reinstated. If the position immediately before the irregularity cannot be determined, the game shall continue from the last identifiable position prior to the irregularity. Articles 4.3 and 4.7 apply to the move replacing the illegal move. The game shall then continue from this reinstated position.

So under the previous rules, if an illegal move was detected only after the game had ended, the game would indeed stand. Unless I am overlooking another relevant article. (I am aware that there are/were multiple types of illegal moves, such as moves played with two hands, but I don't think that makes much difference here.)

If there is a problem now, it seems to me the problem was there already.

I do recognise that the inability of standard PGN to record games with illegal moves (apart from listing the illegal move and the remainder of the game in a comment) may be perceived as a deficiency of PGN. On the other hand, PGN is intended to allow exchange of chess games between computer programs and computer programs typically assume chess games to contain only legal moves. Things would become unhelpfully complex if chess GUIs and chess databases would have to support games containing all kinds of illegal moves. From that point of view, it seems perfectly fine to store illegal moves and whatever follows them as a comment and leave their interpretation to the interested human.

edit: It seems I am repeating what Bajusz Tamás wrote earlier.

[syzygy]

Now that I have read the article linked to in the opening post, I understand that the only change concerns rapid chess.

Under both the old and new rapid rules, an illegal move would stand if not detected before the opponent makes his next move. So in this sense there is no change.

What did change is the consequence of making an illegal move in rapid chess (if detected before the opponent makes his next move). Under the old rules, the opponent would immediately win the game. Under the new rules, the move has to be redone and the opponent only gets a minute extra on his clock.

So the "problem" is that the opponent may now have an incentive not to complain about the illegal move, namely if the illegal move is also a really bad move.

I do not agree that there has been a change in the definition of what it means for a move to be "illegal". A move that was illegal remains illegal; only the procedure of how to deal with illegal moves has changed (in case of rapid chess). The old rapid rules already "embraced" illegal moves in the sense that they would stand unless detected before the opponent made his next move. And the new and old rules for classical chess "embrace" illegal moves in the sense that a game with an illegal move stands if the illegal move was not detected before the game ended. Compare it to a statute of limitations that, on expiry, does not render a committed crime legal, but only prevents the crime from being sanctioned.

[syzygy]

Seems this is the current practice as you can see in twic or in Ed's new millbase .pgn
Here is an example from mb-2017.pgn

That is a nice way to deal with games containing illegal moves. But I would have preferred the continuation game to start from the position after the illegal move (and to give the first move the number 13 instead of restarting from 1).

If PGN has to be extended to deal with games containing illegal moves, I propose replacing the illegal move with a [FEN] tag specifying the new position. Support for such an extension should be relatively easy to implement in GUIs and databases. But it still seems doubtful to me that it would be of much practical value.

[gbtami]

Seems this is the current practice as you can see in twic or in Ed's new millbase .pgn
Here is an example from mb-2017.pgn

That is a nice way to deal with games containing illegal moves. But I would have preferred the continuation game to start from the position after the illegal move (and to give the first move the number 13 instead of restarting from 1).

Agreed.

If PGN has to be extended to deal with games containing illegal moves, I propose replacing the illegal move with a [FEN] tag specifying the new position. Support for such an extension should be relatively easy to implement in GUIs and databases. But it still seems doubtful to me that it would be of much practical value.

Unfortunately endless irregularities can happen in a game. Imagine if in Carlsen - Inarkiev game Inarkiev doesn't stop and they play some more and more moves leaving the black king in check

[syzygy]

Unfortunately endless irregularities can happen in a game. Imagine if in Carlsen - Inarkiev game Inarkiev doesn't stop and they play some more and more moves leaving the black king in check

Then we just have an endless list of FENs . It's better than an endless list of complete PGNs all relating to the same game.

[syzygy]

Does anyone know of a GUI or database or other chess-related software that can deal with arbitrary illegal moves? (I don't think xboard is one of them, unless xboard can deal with Carlsen getting upset and wiping half the pieces of the board and his opponent being too intimidated to protest.)