“…Each of these skills-outcome models can be combined with the models describing how the skills evolve in time. With that regard, the most popular is modelling of the skills via first-order Markov Gaussian processes, e.g., [19], [20], [9], [21], [22], [23], [1], [24], [14], [25]. This formulation is then exploited to derive the on-line rating algorithms in two recursive steps: first, at a time t, the posterior distribution of the skills is found using all observations up to time t; more precisely, to simplify the problem, the Gaussian approximation of the latter is obtained.…”