You could take a look at the ad hoc sub-process for advanced processes where parts of the proces might or might not be executed based on some constraints or user selection.
http://kverlaen.blogspot.com/2010/10/towards-case-management.html
https://github.com/krisv/jbpm/blob/master/jbpm-bpmn2/src/test/resources/BPMN2-AdHocSubProcess.bpmn2
Kris