DMN and CMMN
Two sister standards from omg that cover what BPMN handles badly: decision logic, and work that cannot be laid out as a fixed sequence.
DMN: Decision Model and Notation
DMN separates what is decided from how the process flows. It has:
- Decision Requirements Diagram (DRD): shows decisions, the input data they need and the business knowledge they use.
- Decision tables: rules in rows, with a hit policy that says how multiple matching rules combine.
- FEEL expression language: a standard expression language so logic is executable and portable across tools. OMG also describes an XML interchange format.
Why it matters: when a business rule (credit limit, discount, routing) is buried in gateways, every change redraws the diagram. Moved into a decision table, the business can change the rule without touching the process.
Versions (OMG page): 1.0 Sept 2015, 1.1 June 2016, 1.2 Jan 2019, 1.3 Feb 2021, 1.4 Apr 2023, 1.5 Aug 2024; the page lists 1.6 as the latest formal version and 1.7 as in progress.
CMMN: Case Management Model and Notation
CMMN models case work: knowledge-intensive processes (claims handling, investigations, onboarding) where the next step depends on the case, not a fixed path. Elements include case file items, stages, tasks, milestones and sentries (conditions that open or close parts of the case). Current version 1.1, December 2016 (1.0 was May 2014).
When to use which
| Situation | Use |
|---|---|
| Fixed, repeatable flow | BPMN |
| Complex, frequently changing rules | DMN, called from a BPMN business-rule task |
| Case-by-case, human-driven work | CMMN, or BPMN ad-hoc sub-processes |
Engine support differs: bpm-suites-and-workflow-engines supports BPMN, CMMN and DMN; check each product for what it implements. Decision logic is also a natural tool for AI agents, see ai-and-bpm.
Related
BPM hub, archimate, process-diagram-types
Sources
- OMG DMN specification page: https://www.omg.org/spec/DMN/
- OMG CMMN specification page: https://www.omg.org/spec/CMMN/
- Flowable open source: https://www.flowable.com/open-source