From: anderski@microsoft.com
Subject: RE: SGF definitions
Date: Wed, 29 Jul 92 21:27:19 PDT
Organization: Universitaet Bielefeld

FROM  anderski@microsoft.com , Anders Kierulf
=============================================

> if the move of a player is a 'PASS' the property value is []. e.g.:
> if the white player passes, his move will be coded White[]
> if the white player passes, his move will be coded Black[]
> therefore board sizes upto 26 are possible
> (one can record 21x21 or 23x23 games)

This sounds like a good idea. Programs would still need to
interpret the old definiton for board sizes <= 19, for files in
older formats.

> there is a new property  "CS" : change stones [point list]
> this property will allow to mark prisoners of a move.

Each program reading the Smart Go Board format should
be able to execute legal moves. Storing the prisoners would
raise several problems:
- Is this mandatory? If yes, what about files in an older format?
  If no, what do programs do if this property is not there?
- How does a program recognize whether a file contains the
  "cs" property, or whether simply no stones were captured?
- What if there is a discrepancy between "cs" property and
  actual captured stones?

> there is a new property  "GL" : game length [number]
> this property is only allowed in the root node,
> to present the number of moves of the game

Unnecessary. Easy to determine when the file is read.

> there is the new property "AM" : alternating moves [point list]
> this property collects alternating moves of the players.
> (invented to spend data space) the following 3 lines are equivalent coded:
> ; White[ab] ; Black[cd] ; White[ef] ; Black[qp] ; White[ee]
> ; W[ab] ; B[cd] ; W[ef] ; B[qp] ; W[ee]
> ; AM[ab][cd][ef][qp][ee]
> the last line could be ; AM[abcdefqpee] if one agree (ca. 2 chars per move)

A better option is to have two such properties, e.g. "BW" for sequences
starting with Black, "WB" for sequences starting with White. This would
save space, at the expense of making files harder to read and write by
all programs. Not a clear improvement.

> there should be a special character (e.g. %) to open a one line sgf comment
> . e.g.
> ; Black[cb]  % not sure whether cb or ob

Unnecessary. This format is not designed for human readability. Adding
comments that belong to the file and not to the content raise questions
about what programs reading this format should do to preserve such
comments.

> in the RE property it is recommended to use [W+resign] for a white win by
> resignation or [W-resign] if white resigns. Dito for the black player.
> [W-time] means white losses by forfeit to time.
> [unknown] means that the result is unknown (to the public not to the re-
> corder) and [abort] means there is no result due to abortion of the match.

On the Mac, I use W+infinitySymbol for "White wins by resignation",
and W+(T) for "White wins by time default". W or B followed by a minus
sign is a bad idea: the first letter should always indicate the winner.

Note that changing the file format is not an easy matter: it implies
changing all the programs out there that read the current format.


Anders Kierulf (anderski@microsoft.com)
Newsgroups: rec.games.go