Parallel Gateway

Fork: creates a token on every outgoing flow simultaneously — all branches run in parallel.

Join: waits until all incoming tokens have arrived before continuing. A single parallel gateway element serves as both fork and join depending on how it is wired.

Properties

No condition expressions. All outgoing flows are always activated.

XML Example

<!-- Fork -->
<bpmn:parallelGateway id="fork" name="Fork"/>

<bpmn:sequenceFlow id="branch_a" sourceRef="fork" targetRef="task_a"/>
<bpmn:sequenceFlow id="branch_b" sourceRef="fork" targetRef="task_b"/>

<!-- Each branch has its own tasks -->
<bpmn:userTask id="task_a" name="Task A">
  <bpmn:incoming>branch_a</bpmn:incoming>
  <bpmn:outgoing>to_join_a</bpmn:outgoing>
</bpmn:userTask>

<bpmn:serviceTask id="task_b" name="Task B">
  <bpmn:incoming>branch_b</bpmn:incoming>
  <bpmn:outgoing>to_join_b</bpmn:outgoing>
</bpmn:serviceTask>

<!-- Join -->
<bpmn:parallelGateway id="join" name="Join">
  <bpmn:incoming>to_join_a</bpmn:incoming>
  <bpmn:incoming>to_join_b</bpmn:incoming>
  <bpmn:outgoing>flow_after_join</bpmn:outgoing>
</bpmn:parallelGateway>

Variable Merging at Join

When multiple branches write to the same variable name, the last-arriving branch wins. To avoid conflicts, use distinct variable names per branch.

Notes

• Each fork must be paired with a join that has the same number of incoming flows
• The join uses an atomic counter internally — it is safe under concurrent execution
• For branches where only some paths activate, use an Inclusive Gateway
• The join waits indefinitely — there is no timeout at the gateway itself. Attach a Boundary Timer Event to a task within a branch if you need a timeout