The tutorial just covers domain models created via EMF. However I have no idea how to implement "IIndependenceSolver" or the "Transactional Domain Model"
the editor needs the transactional editing domain already
to make changes to the pictograms model (the diagram).
So even if you do not have a domain model which is
(EMF-) file based but just in-memory you would need to
provide a transactional editing domain for
manipulation of the diagram model.
For opening an editor programmatically you may have a look at
the CreateDiagramWizard class.
If you want to visualize a non-EMF model make sure you deliver an instance
with your FeatureProvider. There, you have to implement
a lookup facility for your domain model objects.
i think a good way to start is implementing an Independence Solver.
You would have to provide a (bijective) mapping between your domain objects
and keys in form of strings. Just have a look at the interface IIndependenceSolver...