Using the understanding of the As-Is Application Model and the As-Is Interface Model the To-Be Interface model is designed in parallel with the To-Be Application model. The two models are tightly coupled and together give a complete picture of the static Application Landscape. It should be noted that the scope of the Interface Model is usually larger than the scope of the Application Model. The Application Model can be a carve-out of the complete Application Model leaving application not in scope out of the picture. The Interface Model is or may also used in applications out of scope and for interfacing to external systems. Some consideration needs to be applied to see if there are constraints that apply to the Interface Model stemming from applications not in scope.

The design process for the Interface Model is largely driven by the requirements that come from the design of the Application Model. The design decisions taken for the Application Model can be shared in the Interface Model. In the design decisions for the Interface Model the constraints that influence the design and originate from applications outside of the scope need to be described.