Chapter 3: OpenAPI and API Specifications

The history of computing has been a long path toward higher and higher levels of abstraction. In the early days of the computer era, computers were programmed with punch cards and assembly languages. The invention of FORTRAN in the 1950s created a programming language that allowed programmers to write code in ways a little more similar to the ways humans work. Over the years, object-oriented languages such as C++ came along and added additional levels of abstraction. In a sense, APIs are another level of abstraction. They allow people to write "code" at a very high level that will tell computers what to do. However, we didn't stop there. As APIs became more popular, we started to develop interfaces that would allow us to specify how an API works, so that users who know nothing about the source code can easily interact with the remote service.

We call these interfaces API specification languages. These languages help with API...