Collapsed embedded subprocesses for overview in large diagrams

Problem description:

Many users have voiced the need to work with embedded subprocesses for gaining better overview in large diagrams.
The idea is that the use of collapsed subprocesses allows to group tasks together and hides them so that is becomes easier to get an overview over the overall flow while having the possibility to "go into" collapsed subprocesses when needed.

This is a bigger research issue and it may turn out that there is no viable end-to-end solution to this at all.

Considerations

• While it would be possible to use Call activities to achieve this, this is not a good solution in all cases since they introduce separate process definitions which is not desirable in all situation primarily due to versioning and runtime implications.
• Any solution found must work seamlessly across all tools in the stack (Modeler, Engine, Cockpit, Operate, Cawemo, Optimize ...)
• Dynamically collapsing / expanding subprocesses won't work since it requires dynamic re-layouting which is not a solvable problem for many reasons unrelated to algorithms
• It makes sense to look at solutions of other tools while we need to take into consideration that most of these won't work in exactly the same way for us since most of these tools do not a) support all of BPMN b) the full BPM lifecycle including Modeling, Execution, Monitoring and Analytics

Some detail questions that need answering

• How to work with message flows that point to elements inside a collapsed embedded subprocess
• How to work with collapsed embedded subprocesses inside collapsed embedded subprocesses
• How do Heatmaps work?
• Cawemo: What if elements inside a collapsed embedded subprocess have comments?
• What if I select the id of an activity instance referencing an activity that is inside a collapsed embedded subprocess in cockpit?
• There are many more