Table 1. Composition of a record in the database. PI: Player of Interest (i.e., player first deviating from a theoretical opening).

Information about	Variable	Values/range
White player	Elo Rating	1600–2399
	Skill level	Class B, Class A, Candidate Masters, or Masters
Black player	Elo Rating	1600–2399
	Skill level	Class B, Class A, Candidate Masters, or Masters
PI	Elo rating	1600–2399
	Skill level	Class B, Class A, Candidate Masters, or Masters
	Color	White or Black
	Relative skill	Weakest (−1) or strongest player (+1) of the pair
	Opening knowledge	Depth of last theoretical move in the game (in ply)
Game duration	Length	Number of moves in the game (in ply)
Outcome	Result	Win for white (1), black (0) or draw (0.5)