Skip to main content

Parallel gateway

A Parallel Gateway is a BPMN flow element that synchronizes parallel flows within a process. It allows a process to split into multiple concurrent paths and synchronize when those paths complete, enabling parallel execution and synchronization of activities.

Key characteristics​

  • Synchronization control: Parallel Gateways split and join concurrent flows, ensuring all branches complete before proceeding downstream.

  • No condition evaluation: Unlike Exclusive Gateways, Parallel Gateways do not evaluate conditions. All outgoing flows are activated when splitting.

  • Token-based execution: Each incoming token creates tokens on all outgoing flows (split). All incoming tokens must arrive before one outgoing token is produced (join).

  • All paths must complete: In join mode, the gateway waits for tokens from all incoming paths. It does not proceed until all branches have sent their tokens.

  • Types of parallel gateway usage:

    • Split (Diverging Parallel Gateway): A single incoming token creates multiple outgoing tokens, one on each outgoing flow. All branches execute concurrently.

    • Join (Converging Parallel Gateway): Multiple incoming tokens are collected. When all paths have sent a token, a single outgoing token is produced.

    • Combined Split and Join (in Loop or Complex Structures): A Parallel Gateway can function as both a split and join in the same process flow, creating loops with parallel branches.

Graphical notation​

Parallel gateway usage example

A diamond shape with a thick plus sign (+) inside.

XML Definition​

<bpmn:parallelGateway id="ParallelGateway_1" name="Split">
  <bpmn:incoming>Flow1</bpmn:incoming>
  <bpmn:outgoing>Flow2</bpmn:outgoing>
  <bpmn:outgoing>Flow3</bpmn:outgoing>
</bpmn:parallelGateway>

Current Implementation​

Current implementation handles parallel flows correctly if there is only one overlapping flow in the process instance. Multiple recursive parallel flows have currently undefined behaviour.