On the Analysis of CMMN Expressiveness: Revisiting Workflow Patterns

Traditional business process modeling languages use an imperative style to specify all possible execution flows, leaving little flexibility to process operators. Such languages are appropriate for low-complexity, high-volume, mostly automated processes. However, they are inadequate for case management, which involves low-volume, high- complexity, knowledge-intensive work processes of today's knowledge workers. OMG's Case Management Model and Notation (CMMN), which uses a declarative style to specify constraints placed at a process execution, aims at addressing this need. To the extent that typical case management situations do include at least some measure of imperative control, it is legitimate to ask whether an analyst working exclusively in CMMN can comfortably model the range of behaviors s/he is likely to encounter. This paper aims at answering this question by trying to express the extensive collection of Workflow Patterns in CMMN. Unsurprisingly, our study shows that the workflow patterns fall into three categories: 1) the ones that are handled by CMMN basic constructs, 2) those that rely on CMMN's engine capabilities and 3) the ones that cannot be handled by current CMMN specification. A CMMN tool builder can propose patterns of the second category as companion modeling idioms, which can be translated behind the scenes into standard CMMN. The third category is problematic, however, since its support in CMMN tools will break model interoperability.