Microsoft Discusses TrueSkill Ranking System

Microsoft has posted extensive details of its TrueSkill Ranking System, to be used on Xbox Live for automatic matching purposes in upcoming games, on the Microsoft Research website. The system is an algorithm designed to accurately report a relative skill ranking after a small number of games played through the service. According to the firm, and unlike the ELO skill ranking system, widely used in chess and other sports, or the system used by Bungie for Halo 2 tracking, the TrueSkill algorithm is a Bayesian one, which calculates a player's skill by his average performance and his average deviance from that performance. The more games a player finishes, the smaller the deviance statistic becomes, and the better the TrueSkill algorithm is able to determine his actual skill. The TrueSkill algorithm is explained in depth at Microsoft's website, which approaches the data from a variety of directions. A FAQ covers all the questions actual players might have, while the more technical and mathematics-oriented System Details page, together with a Ranking System Calculator applet, sets out the nuts and bolts of the TrueSkill system. The system will also be covered in greater depth in an upcoming textbook on Bayesian rankings, from MIT Press.