Due to problems in correctly understanding user requirements the Information System (IS) development community have recognised the need to involve end-users in the development and maintenance of web applications. End-users perceive web applications through user interfaces (UIs) and commonly use sketches of UIs to express their requirements. Thus, it would be desirable to provide an end-user development methodology centred on UI modelling techniques. In this paper a visual modelling approach is presented to empower end-users in developing data intensive web applications starting from user interface descriptions. The modelling language follows a holistic approach by representing both static and behavioural information of a web application in one visual model. The visual model allows the specification of the look-and-feel of the application through mock-ups, and the user interactions through links, annotations, and widget references. End-users are guided during the modelling process by providing a summary view to manage the design of complex applications and a data model view to improve the quality of the generated applications.