Localisation has become a standard feature in many mobile applications. Numerous techniques for both indoor and outdoor location tracking are available today, providing a diversity of ways positioning information can be delivered to a mobile application (e.g., a location-based service). Such factors as the variation of precision over time and covered areas or the difference in quality and reliability make the adoption of several techniques for one application cumbersome. This work presents an approach that models the capabilities of localisation systems and then uses this model to build a unified view on localisation, with special attention paid to uncertainty coming from different localisation conditions and its presentation to the user. We discuss technical considerations, challenges and issues of the approach and report about a user study on users' acceptance of the suggested behaviour of an application based on the approach. The results of the study showed the feasibility of the approach and revealed users' preference towards automatic but yet informed changes they experienced while using the application.

A typical pervasive application executes in a changing environment: people, computing resources, software services and network connections come and go continuously. A robust pervasive application needs adapt to this changing context as long as there is an appropriate rewiring strategy that guarantees correct behavior. We combine the MERODE modeling methodology with the ReWiRe framework for creating interactive pervasive applications that can cope with changing environments. The core of our approach is a consistent environment model, which is essential to create (re)configurable context-aware pervasive applications. We aggregate different ontologies that provide the required semantics to describe almost any target environment. We present a case study that shows a interactive pervasive application for media access that incorporates parental control on media content and can migrate between devices. The application builds upon models of the run-time environment represented as system states for dedicated rewiring strategies.

Users often become frustrated when they are unable to understand and control a pervasive computing environment. Previous studies have shown that allowing users to pose why and why not questions about context-aware applications resulted in better understanding and stronger feelings of trust. Although why and why not questions have been used before to aid in debugging and to clarify graphical user interfaces, it is currently not clear how they can be integrated into pervasive computing systems. We explain in detail how we have extended an existing pervasive computing framework with support for why and why not questions. This resulted in PervasiveCrystal, a system for asking and answering why and why not questions in pervasive computing environments.

Efficient discovery of nearby devices and services is one of the preconditions to obtain a usable pervasive environment. Typical user interfaces in these environments hide the heterogeneity of the environment for end-users which often makes it hard to perceive the provided functionality. We present Pervasive Maps, an approach and tool that allows to create an intuitive user interface for exploring and controlling the environment. Pervasive Maps offers user-oriented views on the user's environment based on pictures of this environment. We show how users can model, explore and finally interact with complex pervasive environments using Pervasive Maps.