Graphical Modeling Framework/GenModel
The transformation of the generator model from the mapping model is described here. If you have looked at the *.gmfgen model that was produced in the tutorial, you'll notice that a quite a few things were created in the process. A general overview of the transformation can be seen in the diagram below, which is followed by detail on each step.
From this diagram, you can see that the selected mapping model is first opened and validated. The canvas is processed, followed by each node, and then each link. Finally, the new generator model is saved and validated.