Model interchange approaches support the analysis of software architecture and design by enabling a variety of tools to exchange performance models using a common schema. This paper builds on the Software Performance Model Interchange Format (S-PMIF), extending it to support the analysis of real-time systems and adapting it to be suitable for implementation with modeling frameworks such as MOF or EMF. This enhances the model interchange process by making it possible to define model-to-model transformations from design models into software performance models. The paper addresses real-time system designs expressed in CCL and their transformation into the S-PMIF for additional performance analyses.