This book presents lectures given at the 8th International Workshop on Spoken Dialog Systems. As agents evolve in terms of their ability to carry on a dialog with users, several qualities are emerging as essential components of a successful system. Users do not carry on long conversations on only one topic¿they tend to switch between several topics. Thus the authors are observing the emergence of multi-domain systems that enable users to seamlessly hop from one domain to another. The systems have become active social partners. Accordingly, work on social dialog has become crucial to active and engaging human¿robot/agent interaction. These new systems call for a coherent