UI Map Sublayer
Principle:
The UI Map sublayer exposes all relevant GUI elements of the SUT to an interface that the functional libraries will use to drive the GUI.
Depending on the automation tool, this might resemble an adapter interface for the automation tool.
Don't be fooled by appearances or neglect the proper implementation of this layer, it is important to keep the functional libraries isolated from the automation tool layer, so any functionality needed by the functional libraries should be implemented in this UI Map layer.
If the developer breaks this layer of abstraction, swapping the automation tool will demand a very large refactoring effort.