Thanks, Lee. Ya, I was making things up with my examples trying to think of reverse roles. The R3 asymmetric phrases was the only one that didn’t feel forced.
I’m a little bugged about including both phrases when they are symmetric. On the plus side, you don’t have to wonder if the omitted one was an oversight or intentionally implied symmetric. On the down side, it clutters the model and violates, ironically, one fact, one place.
Another thing that I run into is not knowing how to say what’s in or out of scope for the model. IOW, just by looking at a model, how can I tell some aspect has been overlooked or if it is intentionally left out? My guess is that the domain diagram and descriptions resolve this issue.
Thanks again, Cort, for providing an example for us to discuss and learn from. I suspect that there are more would-be-xtUML users that struggle to learn because of isolation and lack of mentors.