Safety assurance and certification are amongst the most expensive and time-consuming tasks in the development of safety-critical embedded systems. European innovation and productivity in this market is curtailed by the lack of affordable (re)certification approaches. Major problems arise when evolutions to a system entail reconstruction of the entire body of certification arguments and evidence. Further, market trends strongly suggest that many future embedded systems will be comprised of heterogeneous, dynamic coalitions of systems of systems. As such, they will have to be built and assessed according to numerous standards and regulations. Current certification practices will be prohibitively costly to apply to this kind of embedded systems.OPENCOSS will devise a common certification framework that spans different vertical markets for railway, avionics and automotive industries, and establish an open-source safety certification infrastructure. The strategy is to focus on a compositional and evolutionary certification approach with the capability to reuse safety arguments, safety evidence, and contextual information about system components, in a way that makes certification more cost-effective, precise, and scalable. OPENCOSS will define a common certification language by unifying the requirements and terminology of different industries and building a common approach to certification activities. A fully-fledged tool infrastructure will be developed for managing certification information and performing safety assurance activities. The infrastructure will be realised as a tightly integrated solution, supporting interoperability with existing development and assurance tools. Within this infrastructure, systematic and auditable processes will be developed to reduce uncertainty and (re)certification costs. To have long-lasting industrial impact, we will pursue standardisation of the conceptual framework and the open-source tool infrastructure resulting from the project.