This paper presents a model-based approach for developing vectorial user interfaces to an interactive applications, whether it is a web or a stand-alone applications. A vectorial user interface exhibits the capability of being rescaled in any dimension without any loss of information, while taking advantage of the screen real estate offered by the computing platform on which the interactive application is running. A model describes the vectorial user interface in order to capture its presentation and behavior in a way that is independent of any context of use. Implemented as a browser plug-in, a rendering engine parses this model at run-time so as to render the user interface bounded with the domain, thus producing together a running application. This facilitates platform adaptation, since the interface scales up or down depending on the screen resolution and user adaptation since the model can change from one session to another. The interface is then re-rendered with adaptation for the benefit of the end user. Both platform and user adaptations contribute to making the web application accessible in a ubiquitous way.