xxvi Preface SMART ENVIRONMENT APPLICATIONS Underpinning the promise of smart environments that sense, perceive, interpret, anticipate, and react to events and activities is a confluence of advances in sensing, processing, and networking solutions. Hence, research and development in smart environments offer opportunities in a multitude of disciplines involving sensor fusion, human-centric interfaces, networking, pervasive computing, and responsive environments. Based on the premise of user-centric data extraction and decision making, smart applications support interactivity through interpretation of user gestures, region of interest, and user interactions with the surrounding environment's components. Thanks to the proliferation of inexpensive sensors, including image sensors, and embedded processors, unprecedented potential exists for novel real-time applica- tions such as immersive human­computer interfaces for virtual reality, gaming, tele- conferencing, smart presentations, and gesture-based control, as well as other human-centric applications such as abnormal event and accidental fall detection in assisted living and elderly care. Many user-centric applications benefit from a user behavior model with which the system can tailor its services by learning a user's preferences, habits, and sensi-