Version 3 of SoL introduced a management of players ratings following the Glicko system, mainly to get rid of the random component when generating the first turn couplings in important tourneys.
To put it simply, the system computes a rate of each player that represent the mutual probability of victory: a player rated 2200 will most probably win a match against a player rated 1700.
When a tourney is associated to a particular Glicko rating, the turn generation algorithm takes into account the current rate of each player.
Each rating has a description that must be unique, i.e. it is not possible to insert two distinct ratings with the same description.
The level represent the importance of the rating and its dependability. The rate of a player playing in a tourney associated with a particular rating is his most recent rate in the referenced rating or one with the same level or greater.
The tau is the primary coefficient that drives the computation in the Glicko2 algorithm.
The rate, the deviation and the volatility are the default values of the rate of a player at his first tourney with the given rating.
Important
Only the system administrator is allowed to change these values: usually they should not be modified.
In any case, when these values get changed the rating should be recomputed.