Define "middle-tier". The difference between backend and frontend seem pretty clear to me in the case of web services. Some code is clearly executed in the clie

Define "middle-tier". The difference between backend and frontend seem pretty clear to me in the case of web services. Some code is clearly executed in the client's browser, and the rest is not. You can perhaps use "middle-tier" to be more specific about which aspects of development you mean, but there's no use in fuzzing what is actally a very clear and helpful distinction.