Towards Useful Services for Elderly and People with Disabilities : 9th International Conference on Smart Homes and Health Telematics, ICOST 2011, Montreal, Canada, June 20-22, 2011, Proceedings - Bessam Abdulrazak, Sylvain Giroux, Bruno Bouchard, Hélène Pigot, Mounir Mokhtari ((Lecture Notes in Computer Science))