Bruce Silver: Case Management Model and Notation (CMMN) is the poor stepchild of process modeling standards.  It was developed a decade ago, around the same time as BPMN 2.0.  In case management, the order of actions typically cannot be precisely defined at design time, and many different things happen concurrently.  The list of available actions changes with the state of the case, and initiation of those actions is typically the result of manual case worker decisions.  Link