Dynamically reconfigurable platforms are becoming more and more interesting to design efficient and flexible systems. In addition, real-time applications must satisfy hard constraints to ensure correct execution. To manage such complex systems (hardware and software), the use of an operating system is now a classical solution. However, defining these systems is a tedious task that needs new design methodologies. These methodologies are heavily dependent on the availability of component models. In this paper, the authors propose a component based model of reconfigurable circuits. This model supports the representation of partially and dynamically reconfigurable architectures. It also proposes mechanisms to support heterogeneity of actual components.