As reuse and technology-independence are key issues of both software and web engineering, web services have gained momentum and are heavily used in modern web-based applications. However, they are only expedient for the business logic layer, while the Web lacks uniform models for the encapsulation and reuse of UI components. Thus, web UIs are usually hand-crafted and static, which complicates both development as well as maintenance and upgrade. We address these issues with a novel approach facilitating dynamic, service-oriented composition of user interfaces for web applications. UI parts therein are provided as reusable services and can therefore be selected, customized and exchanged dynamically with respect to a particular context