>As I read the book I knew that type 1 and 2 were oversimplifications They announce as much in the beginning of the book. They said there is overlap between th

>As I read the book I knew that type 1 and 2 were oversimplifications They announce as much in the beginning of the book. They said there is overlap between the different systems and it is an abstraction exercise grouping together various capabilities that do not necessarily fit neatly together. In spite of that, they think it makes sense to consider two different categories broadly speaking.