We present our ongoing work to support the difficult, time consuming, and error-prone process of subsystem integration in the real-time domain. Our work will result in methods where independently developed subsystems, including both hard real-time and soft real-time functions, can be easily integrated without resulting unpredictable timing behaviour. The methods will also facilitate subsystem reuse, since a subsystem can easily be integrated in a new environment. Related research and methods are presented, together with our ongoing work in the area.