The Retrograde Analysis Corner
Jurmala, 2008
(by Werner Keym, Meisenheim)
Update: »Partial Retrograde Analysis« and »Retro Strategy« in the modified Codex
The following new edition of the article 16 of the »Codex for Chess Composition« was resolved at the PCCC meeting on 4th September 2008 at Jurmala (Latvia):
Article 16 – Castling and En-passant capture
(1) Castling convention. Castling is permitted unless it can be proved that it is not permissible.
(2) En-passant convention. An en-passant capture on the first move is permitted only if it can be proved that the last move was the double step of the pawn which is to be captured.
(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).
(4) Other conventions should be expressly stipulated, for example if in the course of the solution an en-passant capture has to be legalised by subsequent castling (a posteriori (AP) convention).
