"Business Logic" is not a layer. Your "Application logic" employs "business rules", but there is no "Business Logic".

Piffle. I don't know where you get that from.

Anything to do with how the business gets run gets coded in one set of class libraries.

Anything to do with an application program gets put in a separate class which asks the "Business Logic" nicely for a favor here and there:

Application Logic asks, "I got a guy here, wants to buy a widget ... what kinds we got, how many of each and what do they cost?"

"Business Logic" responds with the information requested.

Application Logic says, "this guy wants us to pay him to take a small green widget off our hands."

Business Logic replies, "I want some of the drugs he's on".

Get the difference between "Business Logic" and "Application Logic"? Business Logic holds across all applications, but the each application posesses its own logic.

"Business Logic" exists because I say it does, and it works for me to separate it into it's own layer.