Foundations · 02 · 7 min
The shapes that carry 80% of the work
Four categories. Learn the shape language and most diagrams become readable immediately.
BPMN’s shape grammar is consistent: circles are things that happen to the process, rounded rectangles are work the process does, diamonds are decisions about routing, and lines connect them.
Everything below is drawn from those four categories. Click any element to inspect it.
A request is reviewed, then the gateway "Approved?" sends it to "Fulfil request" or "Send rejection", each with its own end event.
The shape grammar, in one table
Four categories, and almost every diagram you will read is built from them. Here is what each one is for.
| Shape | Category | Means |
|---|---|---|
| Circle | Event | Something happens. Border weight tells you when: thin = start, double = intermediate, thick = end. |
| Rounded rectangle | Activity | Work is performed. Always label it verb + object, "Approve invoice", not "Invoice". |
| Diamond | Gateway | Routing only. A gateway never does work and never takes time. |
| Solid arrow | Sequence flow | Order of execution within one pool. |
| Dashed arrow | Message flow | A message between pools. Never inside one. |
Knowing the five shapes is enough to read a diagram. One more habit is what makes the diagrams you write readable to everyone else.
After this module you can
- Identify events, activities, gateways and connectors on sight
- Apply the verb + object labelling rule