Mark Weiser ́s vision of computers moving out of our focus of attention and becoming oblivious devices that occur in large numbers and provide smart computing und communication services to individuals as needed is still far from being reality. This book puts the larger vision of ubiquitous computing in the context of today ́s mobile and distributed computing systems and presents innovative solutions at all system layers ranging from hardware over vertical and horizontal infrastructure services and novel middleware techniques to various types of application software. Some chapters address core properties of ubiquitous applications including mobility, self-healing and self-organisation of both technical and social-technical systems. Other contributions deal with common facilities like secure e-payment or semantic web techniques and business solutions like wireless asset management or e- maintenance. Distributed systems management with self-monitoring capabilities, Internet congestion control, and novel security solutions coping with denial of service attacks against mobile agent systems and software- and hardware-based data encryption methods are further topics addressed.