In domains such as automotive or avionics, software cannot any longer be produced as a single chunk, and engineers are contemplating the possibility of componentizing it. A component only exhibits its provided or required interfaces, which must be enriched to take into account extra-functional aspects. This defines multi-level {\em contracts} between components allowing one to properly wire them. Instead of defining an integrated language only making available a limited set of concepts for modeling extra-functional aspects, we propose to handle open-ended modeling of extra-functional aspects of real-time and embedded systems, based on meta-modeling techniques and Model Driven Engineering (MDE) for reifying their semantics. Then the designer can use off-the-shelf tools to perform various kinds of design time analysis.