1. An enterprise resource planning system comprising an application, a processor, a plurality of business objects, and a backend abstraction layer, where: the backend abstraction layer comprises: a plurality of interfaces for each business object, each interface including a rule identifying a condition on which the interface is to be used; and a plurality of methods for each interface, each method identifying a function to be executed on an external system to the enterprise resource planning system; the application comprises: a plurality of exit points, each exit point containing additional code added to a source code of the application without modifying the source code; and a plurality of connectivity layer reference code included in the application as the additional code contained in each exit point, the connectivity layer reference code providing interactivity between the application and the external system and identifying the business object and method to be executed; and the processor is operative to: execute the source code of the application; upon reaching one of the exit points, execute the connectivity layer reference code included as additional code; identify whether a condition in at least one interface associated with the identified business object is met; when the condition is met, designate the identified method in the identified interface as the method to be executed on the external system.