Figure 12: Model: UML2 composite structure diagram of the monochromator stage assembly with motorised goniometer rotation, tilt, and translation stages, which are driven by encoded devices

Although named after the motorised, controlled values, these are still only the physical blocks. In fact, the upper motion stages will move (they rotate) when the rotating device of the lowest stage (mom) is activated, even though the controlled variables of the upper stages are not even driven. This illustrates an important difference between a low-level logical device view and a physical block view with geometry and relative assembly.