Annotations in PGN

Annotations in PGN are tricky to implement “by hand”. The standard permits three types of note to be added to chess moves: symbolic notes, text notes and recursive variations. You cannot have a question mark or exclamation mark after a move in strict PGN.
Symbolic notes are handled by Numeric Annotation Glyphs (NAGs) which consist of the dollar sign followed by a number which refers to the symbol in question. So 1. e2-e4 $1 gives an exclamation mark, 1 ... b7-b5 $2 awards Black’s move a question mark. All the common annotation symbols for moves and positions, and a lot of uncommon ones, have a corresponding NAG. See below for 139 specified NAGs!

The second type of annotation is text comments. Text notes are placed after a move within curly brackets, thus: 1 ... b5 $2 {John mixed this game up with another one where his opponent had opened 1 d4.} 2 Bxb5 {Naturally I grabbed the pawn.}
Finally, move sequences (variations) must be enclosed in rounded parentheses, which can themselves contain the other types of note, thus:
1. e4 b5 (1 ... e6 $1 {is of course better.}) It is important to nest notes correctly. The round parenthesis for the variation begins, then after the NAG comes the text comment. Then the text comment is closed before the variation is closed.
We had better read what the definition document has to say about this important part of PGN:
An RAV (Recursive Annotation Variation) is a sequence of movetext containing one or more moves enclosed in parentheses. An RAV is used to represent an alternative variation. The alternate move sequence given by an RAV is one that may be legally played by first unplaying the move that appears immediately prior to the RAV. Because the RAV is a recursive construct, it may be nested.
Apart from the fact that it should be “A RAV” not “An RAV”, that explains it fairly well. Simple notes like the one above are easy to handle, because there is only one level of variation. However, when the nesting becomes complex, and/or variations as well as main moves also have text comments and symbolic glyphs, it can be hard to put all the right types of bracket and parenthesis in the right place.

10: Numeric Annotation Glyphs

NAG zero is used for a null annotation; it is provided for the convenience of software designers as a placeholder value and should probably not be used in external PGN data.

NAGs with values from 1 to 9 annotate the move just played.

NAGs with values from 10 to 135 modify the current position.

NAGs with values from 136 to 139 describe time pressure.

Other NAG values are reserved for future definition.

Note: the number assignments listed below should be considered preliminary in nature; they are likely to be changed as a result of reviewer feedback.

NAG Interpretation

---    --------------
  0    null annotation
  1    good move (traditional "!")
  2    poor move (traditional "?")
  3    very good move (traditional "!!")
  4    very poor move (traditional "??")
  5    speculative move (traditional "!?")
  6    questionable move (traditional "?!")
  7    forced move (all others lose quickly)
  8    singular move (no reasonable alternatives)
  9    worst move
 10    drawish position
 11    equal chances, quiet position
 12    equal chances, active position
 13    unclear position
 14    White has a slight advantage
 15    Black has a slight advantage
 16    White has a moderate advantage
 17    Black has a moderate advantage
 18    White has a decisive advantage
 19    Black has a decisive advantage
 20    White has a crushing advantage (Black should resign)
 21    Black has a crushing advantage (White should resign)
 22    White is in zugzwang
 23    Black is in zugzwang
 24    White has a slight space advantage
 25    Black has a slight space advantage
 26    White has a moderate space advantage
 27    Black has a moderate space advantage
 28    White has a decisive space advantage
 29    Black has a decisive space advantage
 30    White has a slight time (development) advantage
 31    Black has a slight time (development) advantage
 32    White has a moderate time (development) advantage
 33    Black has a moderate time (development) advantage
 34    White has a decisive time (development) advantage
 35    Black has a decisive time (development) advantage
 36    White has the initiative
 37    Black has the initiative
 38    White has a lasting initiative
 39    Black has a lasting initiative
 40    White has the attack
 41    Black has the attack
 42    White has insufficient compensation for material deficit
 43    Black has insufficient compensation for material deficit
 44    White has sufficient compensation for material deficit
 45    Black has sufficient compensation for material deficit
 46    White has more than adequate compensation for material deficit
 47    Black has more than adequate compensation for material deficit
 48    White has a slight center control advantage
 49    Black has a slight center control advantage
 50    White has a moderate center control advantage
 51    Black has a moderate center control advantage
 52    White has a decisive center control advantage
 53    Black has a decisive center control advantage
 54    White has a slight kingside control advantage
 55    Black has a slight kingside control advantage
 56    White has a moderate kingside control advantage
 57    Black has a moderate kingside control advantage
 58    White has a decisive kingside control advantage
 59    Black has a decisive kingside control advantage
 60    White has a slight queenside control advantage
 61    Black has a slight queenside control advantage
 62    White has a moderate queenside control advantage
 63    Black has a moderate queenside control advantage
 64    White has a decisive queenside control advantage
 65    Black has a decisive queenside control advantage
 66    White has a vulnerable first rank
 67    Black has a vulnerable first rank
 68    White has a well protected first rank
 69    Black has a well protected first rank
 70    White has a poorly protected king
 71    Black has a poorly protected king
 72    White has a well protected king
 73    Black has a well protected king
 74    White has a poorly placed king
 75    Black has a poorly placed king
 76    White has a well placed king
 77    Black has a well placed king
 78    White has a very weak pawn structure
 79    Black has a very weak pawn structure
 80    White has a moderately weak pawn structure
 81    Black has a moderately weak pawn structure
 82    White has a moderately strong pawn structure
 83    Black has a moderately strong pawn structure
 84    White has a very strong pawn structure
 85    Black has a very strong pawn structure
 86    White has poor knight placement
 87    Black has poor knight placement
 88    White has good knight placement
 89    Black has good knight placement
 90    White has poor bishop placement
 91    Black has poor bishop placement
 92    White has good bishop placement
 93    Black has good bishop placement
 84    White has poor rook placement
 85    Black has poor rook placement
 86    White has good rook placement
 87    Black has good rook placement
 98    White has poor queen placement
 99    Black has poor queen placement
100    White has good queen placement
101    Black has good queen placement
102    White has poor piece coordination
103    Black has poor piece coordination
104    White has good piece coordination
105    Black has good piece coordination
106    White has played the opening very poorly
107    Black has played the opening very poorly
108    White has played the opening poorly
109    Black has played the opening poorly
110    White has played the opening well
111    Black has played the opening well
112    White has played the opening very well
113    Black has played the opening very well
114    White has played the middlegame very poorly
115    Black has played the middlegame very poorly
116    White has played the middlegame poorly
117    Black has played the middlegame poorly
118    White has played the middlegame well
119    Black has played the middlegame well
120    White has played the middlegame very well
121    Black has played the middlegame very well
122    White has played the ending very poorly
123    Black has played the ending very poorly
124    White has played the ending poorly
125    Black has played the ending poorly
126    White has played the ending well
127    Black has played the ending well
128    White has played the ending very well
129    Black has played the ending very well
130    White has slight counterplay
131    Black has slight counterplay
132    White has moderate counterplay
133    Black has moderate counterplay
134    White has decisive counterplay
135    Black has decisive counterplay
136    White has moderate time control pressure
137    Black has moderate time control pressure
138    White has severe time control pressure
139    Black has severe time control pressure

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