A digital environment with a pervasive and unobtrusive intelligence able to proactively support elderly people in their daily lives, enabling them to live independently for longer, and reducing the need for long term care is the fundamental idea of the Ambient Assisted Living (AAL). After considerable research investment, there is a good understanding of the domain problem. However, the need to broaden the scope of problems being addressed is undeniable. Ecological approaches for design and development of AAL services are required in order to reinforce a strong focus on people. The chapter presents a comprehensive model based on the International Classification of Functioning Disability and Health (ICF) to characterize users, theirs contexts, activities, and participation, and to structure a semantic framework for AAL services.