As the variety in network service platforms and end user devices grows rapidly, content providers must constantly adapt their production system to support these new technologies. In this paper, we present a middleware platform for deploying highly interactive (television) applications over a diverse collection of networks and end user devices. As the user interface of such interactive applications may vary depending on the capabilities of the different target devices, our middleware uses UIML for the description of generic user interfaces. Our middleware platform also provides a pluggable support for new networks. A factor that highly complicates the design is the need for strict synchronization between an interactive application and video or audio data that is broadcasted. In order to support a maximum of functionality, downloadable application logic is used to provide the interactive services. As a test case, an evaluation setup was built, targeting both set-top boxes and mobile phones.

The diversity of end-user devices in combination with a growing user base poses important challenges for providing easy access to the huge amount of content and services currently available. Each device has its typical set of capabilities and characteristics that must be taken into account to create an appropriate user interface that provides interactive access to multimedia data and services. Furthermore, end-users also have their specific requirements that influence the accessibility of data and services for individual access. The approach we present in this paper is geared towards the idea of universal access to interactive multimedia data and services for everyone, independent of the user characteristics or end-user device capabilities. For this purpose we combine user and device models with high-level user interface description languages in order to decouple the interface presentation from its platform, and to generate the most suitable interface on a per-user, per- device basis making use of the semantics that are provided by user and device profile.

The wide diversity of consumer devices has led to new methodologies and techniques to make digital content available over a broad range of devices with minimal effort. In particular the design of the interactive parts of a system has been the subject of a lot of research efforts because these parts are the most visible and are critical for the usability (and thus use) of a system. One thing that is missing in many current approaches is the ability to combine these new methodologies and techniques with a user-centric approach to ensure preferences from and requirements for a specific user are taken into account besides the device adaptations. In this paper we analysed the applicability of MPEG-21, part 7: Digital Item Adaptation, for the adaptation of a user interface to user characteristics. We show how the high-level XML-based user interface description language UIML in combination with an MPEG-21-based user profile enables designers to create accessible and personalised multi-device user interfaces. Using this combination results in user interfaces that can be deployed on a broad range of devices while taking into account user preferences with minimal effort. This approach enhances accessibility to digital items on various platforms, since all interactions with digital items should be supported by an appropriate user interface.