Arising from the meeting with @sydb and @HelenaSabel today: we're not 100% clear on whether <rng:ref> elements are created from elements to model classes during the transpile stage. See especially line 153 of transpile.xslt, which kills model classes, versus line 185, where an <rng:ref> appears to be created from them. A test should be added to see what happens and determine if it's what should happen.