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Exclusive gateway

An Exclusive Gateway controls branching and merging of sequence flows based on conditions. When used as a decision point, it evaluates outgoing sequence flow conditions and allows only one to be taken. When used as a merge, it simply passes through the first arriving token without synchronization.

Key characteristics​

  • Condition-based routing: Only one outgoing flow is selected. If multiple conditions evaluate to true, the BPMN specification does not define the selection priority; engines commonly choose the first in model order.

  • Single outgoing token: Exactly one branch is activated during divergence.

  • Default flow support: A default flow may be defined to handle cases where all conditions evaluate to false.

  • Convergence behavior: The gateway does not synchronize multiple tokens; it forwards the first token that arrives.

Usage patterns​

  • Decision (Diverging Exclusive Gateway): Used to model conditional branching (if/else). Each outgoing flow has a condition; exactly one path is selected at runtime.

  • Merge (Converging Exclusive Gateway): Used to merge alternative branches back into a single flow. The gateway forwards the first token arriving from any branch.

  • Conditional routing with default: Define a default outgoing sequence flow to provide a fallback path when no conditions apply.

Graphical notation​

Exclusive gateway usage example

A diamond shape with an X (cross) inside.

XML Definition​

<bpmn:exclusiveGateway id="ExclusiveGateway_1" name="Decide">
  <bpmn:incoming>Flow1</bpmn:incoming>
  <bpmn:outgoing>Flow2</bpmn:outgoing>
  <bpmn:outgoing>Flow3</bpmn:outgoing>
</bpmn:exclusiveGateway>

Current Implementation​

  • Exclusive Gateway is fully supported.