N.B.: yes it's the same layer. HTTP is at the Application layer in the Internet layer model (and this is the Internet, not your school's Network class where the

N.B.: yes it's the same layer. HTTP is at the Application layer in the Internet layer model (and this is the Internet, not your school's Network class where they dream about OSI layers). It's irrelevant which layer this is happening at. The point is that there is a resource address and a resource version. Decoupling those allows you to retain the same resource address for different resource versions - whether this is done for backwards compatibility, multi-language support or other reasons. "All that the author is going to achieve is to have broken client codes every time he's going to bump his API version because most developers won't bother to check the content-type." The point of the article was in fact to teach those mediocre developers who "won't bother", to actually bother to understand these concepts.