In Figure 5.2, module HL1 calls the F() function in module ML1. The fact that it calls this function through an interface is a source code contrivance. At runtime, the interface doesn’t exist. HL1 simply calls F() within ML1.7 Note, however, that the source code dependency (the inheritance relationship) between ML1 and the interface I points in the opposite direction compared to the flow of control. This is called dependency inversion, and its implications for the software architect are profound.
