[Retros] PCCC meeting decisions
liskov at im.bas-net.by
liskov at im.bas-net.by
Sun Oct 25 07:31:30 EDT 2009
Below is the Proposal for Completion of Article 16 of the Codex prepared
by W.Keym and presented at the Meeting of PCCC in Rio (diagrams are
replaced with brackets by me - VL).
==== start
Paragraph 3 of article 16 of the ‘Codex for Chess Composition’ of
September 4th, 2008 runs as follows:
(3) Partial Retrograde Analysis (PRA) convention. Where the rights
to castle and/or to capture en passant are mutually dependent, the
solution consists of several mutually exclusive parts. All possible
combinations of move rights, taking into account the castling
convention and the en passant convention, form these mutually
exclusive parts. IN THE SPECIAL CASE WHERE WHITE’S RIGHT TO CASTLE
EXCLUDES BLACK’S RIGHT TO CASTLE (AND VICE VERSA), AN ALTERNATIVE
IS POSSIBLE: THE PARTY EXERCISING THIS RIGHT FIRST IS ENTITLED TO
CASTLE (RETRO STRATEGY (RS) CONVENTION).
In this paragraph there is a gap concerning certain types of
helpmates (see A–C), as Valery Liskovets found out.
A Armand Lapierre `?’ 1937 [PDB P0533945] H#2. 1.Bc5! 0-0-0.
B Classic example Original [W Kc6 Rc1; B Ke8 Ra8 Rh8] H#1,5.
1.Ra1! 0-0-0
C Luigi Ceriani ‘The Problemist’ 1931 [PDB P0001878] H#3.
Either 1.0-0! or 1.R:h2!
In A, White moved last, therefore w0-0-0 and w0-0 exclude each other.
If w0-0-0 is permitted, then the solution is 1.Bc5! 0-0-0 2.0-0 Rdg1#;
if w0-0 is permitted, then no solution exists. According to the current
codex A is incorrect.
In B, Black moved last, therefore b0-0-0 and b0-0 exclude each other.
If 0-0-0 is permitted, then the solution is 1.Ra1! 0-0-0 2.Ra8#; if 0-0
is permitted, then no solution exists. According to the current codex B
is incorrect.
In C, w0-0-0 and b0-0 exclude each other. If 0-0 is permitted, then the
solution is 1.0-0 a4 2.Kh8 Ra3 3.Rg8 Rh3#; if 0-0-0 is permitted, then
the solution is 1.R:h2 0-0-0 2.R:e2 Rh1 3.Re7 Rh8#. Should this problem
be solved according to the PRA convention? In that case there is one
solution which consists of the two parts 1.0-0 or 1.R:h2. Or should it be
solved according to the RS convention? In that case there is the solution
1.0-0, as Black castles first. Who decides: the author by stating an
additional stipulation or, if he does not do so, the solver by reference?
To fill this gap and to complete article 16, it is proposed to the PCCC
that the following reformulation be substituted for the sentences
underlined above:
IF IN THE CASE OF MUTUAL DEPENDENCY OF CASTLING RIGHTS A SOLUTION IS NOT
POSSIBLE ACCORDING TO THE PRA CONVENTION, THEN THE RETRO-STRATEGY (RS)
CONVENTION SHOULD BE APPLIED: WHICHEVER CASTLING IS EXECUTED FIRST IS
DEEMED TO BE PERMISSIBLE.
This reformulation results in a logical ORDER: in problems with mutually
exclusive castling rights the PRA convention is applied first. If that
does not lead to a solution according to the PRA convention, the RS
convention should be applied.
A has no second partial solution, so it is not a PRA problem. Therefore
the RS convention is applied, with the result that A is a correct RS
problem with the solution 1.Bc5. It is the same in the case of B. This is
a correct RS problem with the solution 1.Ra1. C has two partial solutions
(either 1.0-0 or 1.R:h2) and is a correct PRA problem.
Conclusion:
This reformulation brings nothing but advantages. All cases (w/w, w/b &
b/b castling) are taken into consideration. All PRA and RS problems
remain correct. Treacherous additional stipulations such as PRA or RS
become superfluous.
==== finish
I don't know whether it was published as an article in Die Schwalbe.
WK sent it to me with the following title and foreword (in German):
Vorschlag zur Vervollstandigung des Artikels 16 des Kodex
„Nach der Aenderung des Artikels 16 („Rochade und En-passant-Schlag“)
des „Kodex fuer Schachkomposition“ am 4.9.2008 in Jurmala machte Valery
Liskovets (Minsk) mich auf positive wie negative Folgen fuer bestimmte
Hilfmattprobleme mit einander ausschliessenden Rochaden aufmerksam. Nach
einer Eroerterung mit Retro-Freunden auf der Schwalbe-Tagung am
3.10.2008 und nach intensivem Gedankenaustausch zwischen Valery
Liskovets und mir glauben wir, eine Loesung und Neuformulierung gefunden
zu haben, die den geltenden Artikel 16 vervollstaendigt, indem sie alle
vorhandenen Faelle widerspruchsfrei integriert, naemlich einander
ausschliessende weiss-weisse, weiss-schwarze und schwarz-schwarze
Rochaden im direkten Mattproblem und im Hilfsmattproblem."
V.Liskovets
Joost de Heer <joost at sanguis.xs4all.nl> wrote:
> http://www.saunalahti.fi/~stniekat/pccc/dec09.htm
>
> For retro-composers the following is of importance:
>
> "The last sentence in paragraph 3 of Article 16 of the Codex was modified."
>
> ...
>
> (Does anyone know what changed *exactly*?)
More information about the Retros
mailing list