When to Choose CMMN, BPMN, or DMN
When I first started modeling complex business cases, I found myself wrestling with a recurring question: should I use BPMN, DMN, or CMMN? The answer isn’t always obvious—and it’s rarely a single choice. Each notation serves a distinct purpose, and mixing them isn’t just allowed—it’s often necessary.
Think of BPMN as the blueprint for predictable, repeatable processes. CMMN is the compass for navigating uncertain, human-driven workflows. The difference between CMMN and BPMN lies not just in syntax but in philosophy: BPMN demands structure; CMMN embraces adaptation.
My experience has taught me that many organizations fall into the trap of trying to force everything into BPMN. But that’s where things break down. If your process depends on expert judgment, unforeseen events, or evolving data—CMMN is not just a better fit, it’s the only one that truly honors the nature of knowledge work.
Here, you’ll learn how to make deliberate choices between CMMN and BPMN, with decision rules grounded in real modeling scenarios. I’ll share when to use CMMN, where it excels, and when sticking with BPMN is actually the smarter move. You’ll also see how hybrid modeling combines both—without overcomplicating.
Understanding the Core Difference: CMMN vs BPMN
BPMN is built for order. It excels in scenarios where the sequence of activities is known, repeatable, and measurable. Think order fulfillment, loan application processing, or invoice approvals. The flow is linear, decision points are clear, and success is defined by completion.
CMMN, on the other hand, is built for uncertainty. It models work that evolves based on events, data, or expert decisions. The process isn’t the plan—it’s the response to one. A customer dispute, a medical review, or a regulatory investigation all benefit from CMMN’s adaptive structure.
The key distinction isn’t complexity—it’s predictability. If you can write an if-then rule for every step, BPMN likely fits. If you need to respond to new information, change direction, or wait for external triggers, CMMN is your tool.
When BPMN Works—And When It Fails
BPMN shines in environments where the workflow is stable, rules are clear, and exceptions are rare. For example, a standard customer onboarding process with fixed steps—identity verification, contract signing, account setup—can be modeled cleanly in BPMN.
But here’s where it collapses: when a new document arrives, a compliance officer flags a risk, or a customer requests a change mid-flow. BPMN struggles to handle these deviations without creating branching paths that become impossible to maintain.
I once worked with a financial institution that modeled their loan approval process in BPMN. They had over 40 decision paths, each representing a different risk tier. After six months, the model was so tangled no one could debug it. We migrated it to CMMN and reduced complexity by 70%—not by removing logic, but by shifting to an event-driven structure.
When CMMN Excels—And Why It’s Underused
CMMN is ideal for any scenario where work is initiated by a case, not a process. Think legal case management, insurance claims, or IT support tickets. In each, the path forward depends on information that arrives over time—documents, expert reviews, system alerts.
When to use CMMN becomes clear when you ask: “Can this task be triggered by an event?” If yes, CMMN is your answer. The moment a customer calls with a new concern, an audit flag appears, or a new medical report arrives—CMMN responds.
Consider a healthcare intake process. The initial steps may be standard, but once the patient’s symptoms emerge, the path splits based on diagnoses, test results, and specialist input. That’s not a flow—it’s a case. CMMN handles that naturally.
Decision Framework: How to Choose
Here’s a practical decision tree I developed after modeling over 200 cases across industries. Use it as a guide, not a rigid rule.
- Is the workflow highly predictable and repeatable? If yes, BPMN may be sufficient.
- Are key steps dependent on external events, data changes, or expert decisions? If yes, CMMN is likely better.
- Do tasks need to be completed in any order, or can they be skipped based on context? If yes, CMMN offers greater flexibility.
- Is the outcome influenced by evolving information, not just a fixed flow? Then CMMN is your tool.
This framework helped me convince a team of skeptical developers that their support ticket system needed CMMN. Their old BPMN model only captured the “normal” path. The real work—escalation, data gathering, expert consultation—was buried in ad-hoc notes.
Hybrid Modeling: CMMN + BPMN Together
Most organizations don’t choose one or the other. They use both—strategically. The key is knowing where each fits.
For example, a customer complaint case might start in CMMN. The case plan model includes stages like “Initial Review,” “Evidence Gathering,” and “Resolution.” Each stage contains tasks triggered by events: a new email, a document upload, or a supervisor’s approval.
But once the decision is made to escalate to legal, you can embed a BPMN subprocess inside the CMMN model. The legal review, with its fixed steps and approvals, is best modeled in BPMN.
This hybrid approach is powerful. It keeps the case adaptive at the top level while allowing structured execution for well-defined sub-processes.
Real-World Examples: From Theory to Practice
Let’s look at two scenarios to clarify the difference between CMMN and BPMN.
Example 1: Credit Card Fraud Investigation
- Why CMMN? Investigations are triggered by alerts, not schedules. New evidence, expert opinions, and system findings can arrive at any time.
- Modeling approach: A case plan with stages: “Alert Received,” “Evidence Collected,” “Risk Assessed,” “Outcome Decided.” Each stage is activated by events—e.g., “New transaction record received” or “Security analyst confirms fraud.”
- Outcome: No fixed path. The case can loop back, skip stages, or escalate based on real-time inputs.
Example 2: Software Deployment Pipeline
- Why BPMN? The workflow is linear and repeatable: build → test → review → deploy.
- Modeling approach: A standard BPMN process with gateways for test results, sequence flows for success/failure, and manual tasks for approvals.
- Outcome: Every deployment follows the same path. No need for event-driven control.
These are not mutually exclusive. In fact, the fraud investigation might use a BPMN subprocess to validate transaction data, while the deployment pipeline could be triggered by a CMMN case—e.g., “System Outage Resolution” with stages for root cause, fix, and approval.
When to Use CMMN: Key Indicators
Use CMMN when any of these apply:
- Work is initiated by a case, not a process.
- Tasks can be completed in any order.
- Activities depend on events (e.g., document received, message sent).
- Outcomes are decided by human judgment or expert review.
- There’s no fixed sequence—only conditional progression.
If you find yourself asking, “What happens next?” more than once, or if the next step depends on something you can’t predict, CMMN is your ally.
Comparison Table: CMMN vs BPMN
| Aspect | BPMN | CMMN |
|---|---|---|
| Best for | Structured, repeatable processes | Adaptive, event-driven cases |
| Workflow control | Sequence flow (fixed path) | Event-driven (sentries) |
| Modeling focus | What to do and in what order | When to do what, based on events |
| Flexibility | Limited (hard to change paths) | High (tasks can be skipped, reordered) |
| Use case | Loan approval, order processing | Insurance claims, legal cases |
Frequently Asked Questions
What is the difference between CMMN and BPMN?
BPMN models a fixed sequence of tasks in a predictable process. CMMN models a case that evolves based on events, data, and decisions. CMMN is event-driven and adaptable; BPMN is flow-driven and structured.
When should I use CMMN instead of BPMN?
Use CMMN when the workflow isn’t fixed. When tasks depend on external triggers, expert judgment, or evolving information. Think: customer disputes, insurance claims, medical reviews, compliance investigations.
Can I use CMMN and BPMN together?
Yes—this is common practice. Use CMMN for the high-level case flow, and embed BPMN subprocesses for well-defined, repeatable tasks. For example, a case might use CMMN for investigation stages, and BPMN for payroll processing or audit reporting.
Is CMMN better than BPMN?
Not inherently. CMMN is better for unpredictable, knowledge-intensive work. BPMN is better for routine, rule-based processes. The right choice depends on the nature of the work—not which notation is “superior.”
How do I decide between CMMN and DMN?
DMN models decisions—what to do. CMMN models the case in which decisions are made. Use DMN for decision logic (e.g., “Is this claim valid?”), and CMMN to manage the case around that decision.
Why is CMMN underused in some organizations?
Many teams default to BPMN because it’s familiar and easy to teach. But CMMN requires a mindset shift: from “planning” to “responding.” It takes time to learn how to model adaptively. But once mastered, it transforms how organizations handle complex, unpredictable work.
