# Process Model Complexity

**In short:** A process model can be correct and complete yet too complicated to read. Larger models are harder to understand. Splitting them into subprocesses, limiting data objects, and following guidelines help.

## Explanation

A process model is a diagram that shows how work flows through an organization. Its job is to help people discuss and remember a process. So it must be easy to read and understand. A model can be correct and complete and still fail at this, because it is too complicated.

**Where complexity comes from**

Research shows that larger process models are harder to understand. Measures of a model, such as its size and structure, correlate with how well people understand it. Data objects are one example of clutter. Too many of them overload a diagram, so show only the most important data aspects.

**How to reduce it**

- **Decompose.** Split a large model into smaller subprocess models. This makes the model easier to understand.
- **Choose participants carefully.** For operational models, Camunda recommends a collaboration diagram with a separate pool for each participant, instead of lanes. See BPMN Collaboration Diagram and BPMN Swimlane (Pool and Lane).
- **Follow guidelines.** The Seven Process Modeling Guidelines (7PMG) come from research on how model structure relates to errors and comprehension. They are aimed at casual modelers.
- **Limit data objects.** Use them sparingly.

## Example

Imagine a collaboration with three participants: a customer, a bank, and a registration office. One diagram shows every task, every check, and every document. Nobody can follow it. The team keeps a top-level diagram with one step per phase. Each phase opens into its own smaller subprocess diagram. Only the few data objects that matter, such as a payment confirmation, appear.

## Trade-offs

Simplification must be weighed, not applied blindly. Structuredness, meaning a clean and regular model structure, is not an absolute rule for understandability. Trade-offs with other model properties exist. Splitting a model also gives you several diagrams to keep consistent.

BPMN diagram: [A top-level process kept simple by moving detail into a subprocess.](https://arc.fuet.ch/diagrams/concepts/modeling-bpmn/process-model-complexity/diagram-1.bpmn)

## Checks

- Large process models are split into smaller subprocess models.
- Data objects are limited to the most important data aspects.
- Operational models use separate pools per participant rather than lanes.
- Modeling guidelines such as 7PMG are applied or consciously deviated from.

## Related

- [BPMN 2.0 Model Quality](https://arc.fuet.ch/concepts/modeling-bpmn/bpmn-2-0-model-quality.md)
- [BPMN Modeling Guidelines](https://arc.fuet.ch/concepts/modeling-bpmn/bpmn-modeling-tips.md)
- [Levels of Process Modeling](https://arc.fuet.ch/concepts/modeling-bpmn/levels-of-process-modeling.md)
- [BPMN Collaboration Diagram](https://arc.fuet.ch/concepts/modeling-bpmn/bpmn-collaboration-diagram.md)
- [Complexity Reduction](https://arc.fuet.ch/concepts/principles/complexity-reduction.md)
- [Core BPMN Element Subset](https://arc.fuet.ch/concepts/modeling-bpmn/bpmn-element-usage-frequency.md)
- [BPMN Data Element](https://arc.fuet.ch/concepts/modeling-bpmn/bpmn-data-element.md)
- [Fitness for Purpose](https://arc.fuet.ch/concepts/evaluation/fitness-for-purpose.md)

## Sources

- [AIS Electronic Library (AISeL) - ICIS 2014 Proceedings: Testing the Impact of Wand and Weber’s Decomposition Model on Process Model Understandability](https://aisel.aisnet.org/icis2014/proceedings/GeneralIS/28/) — aisel.aisnet.org, accessed 2026-11-09
- [Creating readable process models | Camunda 8 Docs](https://docs.camunda.io/docs/components/best-practices/modeling/creating-readable-process-models/) — docs.camunda.io, accessed 2026-11-09
- [Understanding business process models — Eindhoven University of Technology Research Portal](https://research.tue.nl/p/en/research-outputs/understanding-business-process-models-the-costs-and-benefits-of-s) — research.tue.nl, accessed 2026-11-09
- [Seven process modeling guidelines (7PMG) — Eindhoven University of Technology Research Portal](https://research.tue.nl/p/en/research-outputs/seven-process-modeling-guidelines-7pmg) — research.tue.nl, accessed 2026-11-09