The functionality of the parallel gateway is based on the incoming and outgoing sequence flow(s):

An important difference with other gateway types is that the parallel gateway does not evaluate conditions. If conditions are defined on the sequence flow connected with the parallel gateway, they are simply ignored.

The actual behavior (fork, join or both), is defined by the sequence flow connected to the parallel gateway.

For example, the model above comes down to the following XML:

When these two tasks are completed, the second parallel gateway joins the two executions and, as there is only one outgoing sequence flow, no concurrent paths of execution are created and only the Archive Order task is active.

Note that a parallel gateway does not need to be ‘balanced’ (i.e., a matching number of incoming/outgoing sequence flows for corresponding parallel gateways). A parallel gateway will simply wait for all incoming sequence flows and create a concurrent path of execution for each outgoing sequence flow, not influenced by other constructs in the process model. So, the following process is legal in BPMN 2.0:

Camunda Extensions

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