A smart space offers entirely new opportunities for end users by adapting services accordingly to make life easy. A number of architectural designs have been proposed to design context awareness systems and adaptation behavior. However, the quality of the system depends on the degree of satisfaction of the initials needs. In this paper, we discuss three main indicators of quality design for smart spaces that are strongly related to the context modules and reasoning process: functionality, reusability and changeability. A general layered architecture system is presented to define the principal components that should constitute any context aware adaptive system.