[Retros] PRA & RS: Jurmala-2008 vs Piran-1958

[raosorio at fibertel.com.ar]

Hi friends,

I see the following points:

1) From the very beggining, we should note that the Code in art 2 establishes
"A chess composition consists usually of a POSITION on the chess board".
So, it does not refer to a DIAGRAM (which is just a distribution of pieces on the
board) but to a POSITION. the Code does not define what is it, but it is well 
establish that a position is diagram+ rights. 

If we start from here, then there are two completely different situations:

a) A helpmate position where both O-O and O-O-O are posible but mutually
exclusive and there are two potential solutions based one to one on each of them.
Since the problem starts from a "position" , the first solution the solver shows
determines the choice of the used castling right and the other one is not posible
starting from the same "position" (unless RVs were mentioned).

b) A twinned problem like P.R. Orlik, 1978 [P0534191]. Twins start by nature from
different positions since the distribution of pieces on the board are not the same,
so they result from different proofgames. Therefore, the a) and b) solutions in this
type of problems have no special considerations.

2) In any problem, the initial position and all the intermidiate ones during the
solution sequence have to be legal. So, why is the "RS convention" necessary?
Isn't it obvious that, if black and white castling rights are mutually exclusive, then 
any side is abble to do it but after one of them doing it the other has no more the
right (since it would be illegal)?

Best,
Roberto



----- Mensaje original -----
De: Valery Liskovets <liskov at im.bas-net.by>
Fecha: Viernes, Septiembre 19, 2008 6:30 am
Asunto: Re: [Retros] PRA & RS: Jurmala-2008 vs Piran-1958


> Joost de Heer wrote:

> 

> > Has anyone made a comparison between the previous article and 

> the current

> > one?

> 

> For comparison, we should now, apparently, stipulate not applying

> the PRA-convention (Art.16.3) to ordinary helpmate problems

> like the following: P.R. Orlik, 1978 [P0534191]

> W: Ke1 Ra1 Rh1; B: Kg2 Rc2 Rg3 Sd4 Se4 (3+5) h#2 b) bKb3

> a) 1.Rf2 0-0-0 2.Rgf3 Rdg1#; b) 1.Rgc3 0-0 2. Kb2 Rfb1#.

> 

> Valery L.

> 

>