The invention relates to a method of classifying a plurality of activities associated to a user. The method comprises receiving first activity data indicative of a first activity performed by the user during a first time interval, the first activity data comprising a plurality of measurements associated to at least one first parameter monitored during the first activity； receiving second activity data indicative of a second activity performed by the user during a second time interval, the second activity data comprising a plurality of measurements associated to at least one second parameter monitored during the second activity, the second activity different to the first activity； a processor comparing at least some of the first activity data and at least some of the second activity data with respective sets of measurements stored on a tangible computer readable medium； a processor generating a set of observation alerts based at least partly on the comparison of the first activity data and the second activity data with the respective sets of measurements； a processor comparing the set of observation alerts with respective sets of observation alerts stored on a tangible computer readable medium； and on detecting a match between the set of observation alerts and at least one set of the stored observation alerts, a processor generating at least one inference alert. The invention also relates to similar systems and computer-executable instructions.L'invention concerne un procédé de classification d'une pluralité d'activités associée à un utilisateur. Le procédé comprend les étapes consistant à recevoir des premières données d'activité indicatives d'une première activité effectuée par l'utilisateur pendant un premier intervalle de temps, les premières données d'activité comprenant une pluralité de mesures associées à au moins un premier paramètre surveillé pendant la première activité ； à recevoir des secondes données d'activité indicatives d'une seconde activité effectué
