The design and development of Graphical User Interfaces for Rich Internet applications are well known difficult tasks with current tools. The designers must be aware of the computing platform, the user's characteristics (education, social background, among others) and the environment within users must interact with the application. We present a method to design theses type of User Interfaces that is model-based and applies an iterative series of XSLT transformations to translate the abstract modeled interface into a Final User Interface that is coded in a specific platform. In order to avoid the proprietary engines dependency for designing tasks. UsiXML is used to model all the levels. Several model based technologies have been proposed and in this study we review a XML-compliant User Interface Description language: XAML.