Abstract. This paper explores an architecture for very long term user modelling, based upon personal user model clouds. These ensure that the individual’s applications can access their model whenever it is needed. At the same time, the user can control the use of their user model. So, they can ensure it is accessed only when and where they wish, by applications that they wish. We consider the challenges of representing user models so that they can be reused by multiple applications. We indicate potential synergies between distributed and centralised user modelling architectures, proposing an architecture which combines both. Finally we discuss implications of our approach for consistency and freshness of the user model information.