[Retros] MDR

[raosorio at fibertel.com.ar]

Hi Valery and Andrew, 

Some remarks after your last postings (the lack of the MDR presenting article 
is of course complicating the things. Hope we'll be abble to publish it soon),

a) MDR is a diagram convention that, on the contrary to the (CODEX art.14 (2), accepts
     the POSIBILITY of an illegal move on the last (just the last) move. The existence of
     an illegal move has to proved by retroanalysis (equivalent to the e.p. capture right).
     If the position could be legal then it is legal. Say that MDR tries to minimyze the
     deviation from the rules, and legallity is no deviation.
     Very nice twinnings are posible based on this.

b) In case of illegality, the 7.4 retraction automatically applies and the forward play is
     conditionated by the article 4 consequences. The MDR definition stablishes as a
     restriction that the illegal move has to be of the "geometrically correct type", which
     means that the move follows the article 3 geometry. Illegalities to the "turn to play"
     and "passing over another piece (not being a knight)" are not allowed. Otherway, 
     the diagram would be an inferno, and the idea is to strenght the retrothinking but
     not insanity.

c) MDR is a base for retroproblems. Therefore,  the laws stopping the game automatically
    apply. Then, there are no after mate moves nor after DR ones.

d) Incompletion: an illegality source. Incompletion is related to those
     moves that involve more than one piece. The diagram is the result of a FYNALYZED
     move (in real game, the player pressed the clock), so these would be "geometrically
    correct, fynalyzed and incomplete" moves. These are clearly prevented by article 4.6,
    which forces to make the complete move. Ke1-g1 is an example (please note that
    without the h1 rook this move is not geometrically correct).

e) Opportunity: the other illegality source (please note that it's Opportuniy, not "Opportunities")
     Perhaps this is not a happy translation from the spanish "Oportunidad" (Andrey, help me), 
     meaning that "this is not the time to do this" (due to check)  or "you have already lost your chance"
     (for instance castling when you have already lost the right to do it). Article 4.1-4.5

f) The MDR name: the basic concept here is the Minimal Deviation one, including even
    legal situations. Article 4 are the consequences and, when they are not relevant,
    they are not part of the MDR problem  (we have compossed some examples)

g) Antecedents: of course we'll discuss in the article the BG concept as an antecedent.  
    BG and MDR should be kept separated anyway due to the following reassons,
     g.1) MDR is a diagram convention and the illegality has to be found in the retroplay
            while BG makes posible the "touched-moved" trick in the forward play, as shown
            in some wonderful Valery's problems.
     g.2) BG focusses on the article 4 consequences and MDR on the Deviation, as discussed
             before.
     g.3) As valery stated,  "only one ORDER OF TOUCHING PIECES while capturing (at least e.p.) 
           is admitted: first the own capturing piece, then the opponent's one to be captured... "
           This applies to BG, while MDR definition stablishes two types: "Technical Type (coincident
           with the BG one)" and "Romantic Type (where both orders to touch the pieces are accepted
           as RV)". This was used in our polemyc Die Schwalbe problem 13071.
     
Best,
Roberto


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Dear retro-friends, 

Two passing remarks on this fruitful discussion. 

1. Jorg Kuhlmann's award for fairies in Die Schwalbe 228 is now available at 
http://www.dieschwalbe.de/unserezeitschrift/aktuelledieschwalbe/aktuelleschwalbe.html 

2. In the PDB, I found 15 problems based on the rules of touching pieces 
(beruehrt - gefuehrt, or BG). Among them: 
2 are with illegal positions (including the earliest one by Trillon, 1969); 
12 are with ep-keymoves; 
2 are of FAIRY genre retro-volages (with a proper modification of this 
rule wrt recoloring pieces proposed and briefly described by me). 

Among the 12, 5 problems published in 1981-89 (including 4 mine) 
strongly depend on the additional assumption that in composition, 
by default (or otherwise to be stipulated explicitly), only one ORDER 
OF TOUCHING PIECES while capturing (at least e.p.) is admitted: 
first the own capturing piece, then the opponent's one to be captured... 

Valery Liskovets 
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Hi Roberto, 

Thanks for your mail. Maybe determining criteria is less problematic that I had 
thought. I don't know though. 

You say that overlooking check is an "opportunity". But overlooking mate is 
not? What's your logic there? How about if a player makes a move out of turn? 
Or (subtle difference) if a player passes without having moved? After Kf1-g1, 
is it an opportunity error to complete the move with Rh1-f1? 

I appreciate that the legality of the diagram is not at question for this 
format. My remark on proof games was a more general one, in response to the 
idea that fairy pieces + pawns =< 8. 

I find the terminology "MDR" a little dull. There are too many acronyms in this 
little hobby anyway. May I suggest "Red-Handed" as a lively phrase which (in 
English) exactly captures your idea? 

Andrew.