Wrapping up before going back to the demo

In this chapter, we have learned about the SOLID principles that can be applied to information systems (and not only object-oriented programming, as they were initially aimed at); the single responsibility principle and the interface segregation principle have been used to start a definition of the different API contracts we will need for our demo application. The open/closed principle will help to keep this API grammar free to evolve, and its evolution will have to follow the Liskov substitution principle for the system to evolve satisfyingly. Finally, dependency inversion has been demonstrated as the core principle behind contract-first API and the capacity to align the software implementations on the business-oriented functions, which is the main goal we seek in this book.

In the next chapter, we will go one step further in the design of our demo application by defining its different components. This will help us to draw a perimeter of...