Many studies have been conducted in order to develop systems that respond to user requirements in domotic environments. These systems generally offer predefined scenarios corresponding to general requirements and enable users to select those he/she wants to trigger. We claim that such behaviors cannot be hardwired: user scenario definition should be supported. In this article, we propose the specification of a component-based domotic system that tackles this issue. This system automatically detects available devices in the environment and offers users high level Guis to define their own scenarios from functionalities of the detected devices. These scenarios are then automatically implemented by the system: components are generated from device descriptors, assembled as prescribed by the scenarios and the resulting software is run by a rule execution engine