Sharing heterogeneous data among distributed environments in a user- centric way represents today the main challenge for personalization. In recent years several techniques have been proposed to support user mod- eling for multi-application personalization. In this paper we describe G- Profile, our multi-application user modeling system. G-Profile represents a way to address some open issues not sufficiently investigated in litera- ture, as the opportunity for a multi-application profile to evolve over the time, together with the possibility to guarantee security and privacy in the diffusion of user information among applications. In particular, this paper focuses on user profile data modifications propagation, aiming to reduce the amount of incoherent information about the user over several applications.