@lovlas Here is a mathematical model:
http://glicko.net/glicko/glicko2.pdfNote especially:
To apply the rating algorithm, we treat a collection of games within a “rating period” to have occurred simultaneously. Players would have ratings, RD’s, and volatilities at the beginning of the rating period, game outcomes would be observed, and then updated ratings, RD’s and volatilities would be computed at the end of the rating period (which would then be used as the pre-period information for the subsequent rating period).
Note that OGS implemented an improved version of Glicko-2; here is that announcement:
forums.online-go.com/t/ogs-has-a-new-glicko-2-based-rating-system/13058