So far, little research has addressed reuse and contextawareness with respect to rich web-based user interfaces. Uniform models for encapsulation and reuse have been developed for the applications’ back ends in the form of Web Services, but this paradigm has not yet been applied to the presentation layer. Thus, UIs are usually hand-crafted and lack flexibility and reuse, which makes their development time- and money-consuming. We address these issues with a system facilitating dynamic, service-oriented composition of user interfaces for modern web applications. UI parts are provided “as-a-service” and can thus be selected, customized and exchanged with respect to the current context.