7.1. Coupling Explained

The term “coupling” is a pretty straight-forward part of the IT vocabulary: Anything that connects has coupling and coupled things can form dependencies on each other. However, when we qualify coupling with “loose” or “tight,” we get into a more ambiguous realm. Who’s to say what is considered more or less dependent? We will need a firm understanding of how to measure and allocate appropriate levels of coupling (Figure 7.1) in order to effectively apply this principle. Let’s therfore begin with a brief exploration of how coupling relates to automation environments in general.

Figure 7.1. This principle emphasizes the reduction (“loosening”) of coupling between the parts of a service-oriented solution, especially when compared to how applications have traditionally been designed. Specifically, loose coupling is advocated between a service contract and its consumers and between a service contract and its underlying implementation.