The recent advances in Unified Modeling Language (UML) give a valuable milestone for its application to modern embedded systems design space exploration. However, it is essential to remember that UML is unable to solve the difficulty associated with embedded systems analysis, but it only provides standard modeling means. A reliable Design Space Exploration (DSE) process which suits the peculiarities of complex embedded systems design is necessary to complement the use of UML for design space exploration. In this article, we propose a Model Driven Engineering-based (MDE) co-design flow that combines high-level data-intensive application analysis with rapid prototyping. In order to specify the embedded system, our methodology relies on the Modeling and Analysis of Real-Time and Embedded Systems (MARTE) UML profile. Moreover, the present contribution uses the Parameterized and Interfaced Synchronous Dataflow (pSDF) Model-of-Computation (MoC) and a model based on the IP-XACT standard as intermediate levels of abstraction to facilitate the analysis step in the co-design flow. The rapid prototyping process relies on the pSDF graph of the application and a system-level description of the architecture. This paper presents our Hw/Sw cospecification methodology, including its support for gradual refinement of the high-level models towards lower levels of abstraction for design space exploration purposes.