Toby,
http://buzzword.org.uk/2009/domain-range-illustration.pngIt would be even better to flip it so that the ontology level is on top of the instance level, so to be in line with MOF.You're right, it's much clearer this way: http://buzzword.org.uk/2009/domain-range-illustration-flipped.png
Great :-) I will hand this out to my students next time, let's see if they get it right :-)
Best, Bernhard