The below architecture diagram shows the type of layered application. The business layer is where all the business/domain logic, i.e., rules that are particular to the application's problem, has been built to handle. It should be noted here that here the business layer defines the data structure. These can be complex, so the core data structures should be defined and solely focused on the business problem. For instance, validation of data often flows up to the Presentation Layer to get early feedback. It may also flow down to the database to ensure database integrity.
