User interfaces for ubiquitous augmented reality incorporate a wide variety of concepts such as multi-modal, multi-user, multi-device aspects and new input/output devices. In this paper we present a twofold approach that consists of an execution engine for ubiquitous augmented reality user interfaces and a runtime development environment that enables rapid prototyping and live system adaption for such advanced user interfaces. Categories and Subject Descriptors: H.5.2 User Inter