[Retros] 50 moves rule

[Rol, Guus]

Yes, that is an important question. To undercut this discussion I have
used "positional properties" rather than "position" in my comments.
Surely castling and e.p. rights are properties of positions. For me
"positions" are synonym to "states". States contain are all present time
information of a system pertaining to possible future developments.
Besides the usual suspects "diagram", "castling/e.p. rights" there are
also more obscure factors involved like "how far we advanced in the 50
moves count" and "all positions eligible for repetition + repetition
counts". In my comment to Tom Volet I argued that it would be unwise to
include the latter two in the evaluation cycle of the the
50-moves/repetition rules since that would lead to oscillating
evaluations - the evaluation process affects its own outcome.

Going into specifics, one might think that the analytical impossibility
of future castling conforms to the state requirement of being "incapable
to affect the future developments in the game". If that were the case,
then the castling right propery in such positions would have to be
denoted as "false". However, a repetition query of that nature was
raised (I think somewhere in the 1960s)in actual tournament practice
with the well-known move sequence
Sd5-c7+,Ke8-e7,Sd5+,Ke8,Sc7+,Ke7,Sd5+,Ke8,Sc7+ draw? The resounding
arbitration was NO! I tricked you slightly by adding the last move Pc7+
which was redundant in the original issue. It was appended to conform to
your wish to look at a position in which (a) castling right was
initially present (b) castling has become an impossible future option
(c) a termination criterium (triple repetition) was apparently met. The
verdict shows that the FIDE has chosen to look at castling right as
statutory (I hope this the appropriate english designation) chess law.
In other words "the condition of castling right is not dictated by the
possibility to execute castling at some point"; I assume the same is
true for en passant. This is probably a very wise decision as it keeps
the need to analyze positions away from the rules. Also, it is easy to
create ambiguous situations between castling rule and 50-moves rule if
you choose the other option. Even when I adopt a highly provocative
approach to the FIDE/Codex building, it is not my intention to destroy
the premises. Just to improve the living conditions.

Guus Rol.


-----Oorspronkelijk bericht-----
Van: retros-bounces at janko.at [mailto:retros-bounces at janko.at] Namens
Seth Breidbart
Verzonden: vrijdag 5 januari 2007 20:40
Aan: retros at janko.at
Onderwerp: Re: [Retros] 50 moves rule


It seems to me that the underlying issue is the definition of
"position".  Is it a photograph of the pieces on the board?  That plus
information as to whose move it is?  That plus information as to who
might be allowed to castle (and on which side) in the future? (Consider
a position in which White has not castled, his King and Rooks have not
moved, but it can be proven that there is no future play which involves
White castling; how does that count?)

Seth
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