Résumé : When developing real-time systems such as avionics software, it is critical to ensure the performance of these systems. In general, deterministic Quality of Service (QoS) is guaranteed by the execution platform, independently of a particular application. For example, in the avionics domain, the ARINC 664 standard defines a data network that provides deterministic QoS guarantees. However, this strategy falls short of addressing how the QoS requirements of an application get transformed through all development phases and artifacts. Existing approaches provide support for QoS concerns that only cover part of the development process, preventing traceability. In this paper, we propose a declarative approach for specifying QoS requirements that covers the complete software development process, from the requirements analysis to the deployment. This step-wise approach is dedicated to control-loop systems such as avionics software. The domain-specific trait of this approach enables the stakeholders to be guided and ensures QoS requirements traceability via a tool-based methodology.