I find the implementation of call activity in ARIS a bit exotic. I would be happy to learn from the community how do you go about it. The occurrence/definition concept and assignment/selectionOfGlobalActivity pose some challenges.
1. My first question is do you use definition or occurrence copies?
My preference is for definition because call activities calling the same global activity from different processes can bring different input. But that's a high-maintenance option and a double work when modelling and changing. Additionally having deffintion copies with the same Name poses other problems.
Using occurrence copies seems easier but is it BPMN2-complient, how do you know who is calling (without checking in which model is the occurrence) and then what about execution?
2. The second question is related to selection of global activity. What is now allowed is to select a task or a collaboration diagram but not the most common IMO thing - the process diagram. Do you also find it strange and what do you do about it.
I few other things related to BPMN2-in-ARIS have been bugging me the last couple of years, but let's not bee greedy.