use a URI based import for refering files to import rather than use project scope
In order to have several models in the same eclipse project, it would be more comfortable to use a URI based import to be able to create the list of files to consider.
https://blogs.itemis.com/en/in-five-minutes-to-transitive-imports-within-a-dsl-with-xtext
This would prevent from mixing unwanted model elements and create a cleaner dependency graph