computer-go: Saving Go Problems in SGF

["Pierce T. Wetter III" <pierce@xxxxxxxxxxxxxxxxxx>]

(See Go Problem Background email first)

There is the following set of "extra" information needed for a problem 
vs. a game that needs to be saved if we don't want to lose information 
when moving from TW's format to SGF.

  1. What strings to save/kill.

  2. The best variation for White.

  3. The best variation for Black.

  4. [optional] other, less optimal variations

  5. result of the variation.

 SGF doesn't really allow this, but there are some possible workarounds 
(note that I knew nothing about SGF before yesterday, and probably 
others have run into this problem, so perhaps they have better 
solutions...)

  a. First off, store an application property AP[GoProblem] tag in the 
file, so that programs reading the file will know that whatever 
conventions we come up with will apply.

  b. To accomplish 1, mark the strings to save/kill with a triangle (TR).

  c. To accomplish 2 &3, put the White/Black best variations first in 
the tree, and mark those variations with GW and GB (good for white, good 
for black)

  d. Other variations would just be stored as branches of the tree.

  e. The result could be stored in a C or N tag (Comment or Name) in a 
special format, or perhaps a new node property could be created: "LD" 
for life/death. So LD[l2d] means whoever moves first lives, but will die 
with 2 threats. Conversely, the C or N field could be english readable 
but easily parseable:  C[White lives but dies with 2 external threats].

 Comments?

 Pierce