Facebook, Gmail and Dropbox are only three examples of successful web applications. Each of them provides specif ic functionalities and application composition allows user to extend the range of functionalities they can benefit from. However, they rely on mediation code produced by expert developers. As a result, end users cannot freely compose web applications. They cannot precisely configure their privacy preferences either. These two constrains impair users experience. Our work seeks to deal with this lacks. We propose a model-driven approach which permits end users to specify the composition of their web applicati ons and their privacy preferences. Our approach allows to generate the execution code so that end users do not have to rely on developers. Our work is implemented as a modeling and execution tool. We use our tool to realiz e a real - world composition