Thanks, Dann. Always a pleasure to release something that can be useful to other people in the computer chess community.

Most of the EPD simply follows the EPD part of the PGN standard:
https://opensource.apple.com/source/Chess/Chess-109.0.3/Documentation/PGN-Standard.txt
(See section 16.2).

However, I add my own fields:
cce is computed centipawn evaluation which is based on wins/losses and draws.  I did a parabolic least squares fit to approximate the computer scores.
white_wins black_wins and draws are the number of games with particular outcomes in my filtered game database (not all games have outcomes, some are *)
I use pm in a non-standard way.  The PGN Standard says that the pm is just the first node of the pv, but I consider that both redundant and useless.  I use pv as the collection of the most likely moves to be played.  If there is a number in curly brackets after the suggested move, that number is how often the move was actually played.

So, given this:
pm Nc6 {9274} Nf6 {4553} g6 {3298} b6 {654} e6 {588} e5 {400} d6 {35} d5 {4} a6 {3} Na6 {2} f5 {2} b5 {1} h6 {1}; pv g6 g3 Bg7 Bg2 Nc6 e3 e6 Nge2 Nge7 O-O O-O d4 cxd4 exd4 d5 cxd5 Nxd5 Re1 Qb6 Na4 Qd8 Nac3; white_wins 6593; black_wins 5528; draws 6011; Opening English Opening: Symmetrical Variation. Normal Variation 1.c4 c5 2.Nc3; CaxtonID: 523; ECO: A34;

Postition, side to move, castle rights and ep status:


Other fields are described here:
acd 36; means the depth of the analysis was 36 plies
acs 148; means that the position was analyzed for 148 seconds
bm g6; means that g6 appears to be better than other moves.
c3 "Nf6" means that I was studying Nf6 at some point or the position appeared in a famous game and Nf6 was played.  I use that comment field to hold suggested moves for study.
cce -26; means that in actual game outcomes, black is behind by about 1/4 pawn
ce 0 means the computer says the position is even
id "es-dc-neutral.0524"; means it is contained in the test set es-dc-neutral (a collection of severely balanced openings)
pm Nc6 {9274} Nf6 {4553} g6 {3298} b6 {654} e6 {588} e5 {400} d6 {35} d5 {4} a6 {3} Na6 {2} f5 {2} b5 {1} h6 {1};  means that Nc6 is the most likely move, followed by Nf6, and g6
pv g6 g3 Bg7 Bg2 Nc6 e3 e6 Nge2 Nge7 O-O O-O d4 cxd4 exd4 d5 cxd5 Nxd5 Re1 Qb6 Na4 Qd8 Nac3; is the computer plan for this position
white_wins 6593; black_wins 5528; draws 6011 are simply the game outcomes from my database for this position
Opening English Opening: Symmetrical Variation. Normal Variation 1.c4 c5 2.Nc3; CaxtonID: 523; ECO: A34; is the name and description of the opening