A predefined user interface definition specifying a first service is accessed in persistent storage. The user interface definition includes an extension including a fragment definition specifying a second service. First content is retrieved from the first service according to the user interface definition. Second content is retrieved from the second service according to the fragment definition. A user interface is rendered in a display space according to the predefined user interface definition and including the first content and the second content. At least one of the accessing, the retrieving first content, the retrieving second content, and the rendering is performed by at least one data processor forming part of at least one computing system. Related apparatus, systems, techniques and articles are also described.