InclusiveGateway , ComplexGateway and ParallelGateway must have at least two outgoing SequenceFlows.


Gateways are control nodes that control in which direction the sequence will continue, therefore they must have at least two outgoing paths. ParallelGateways and ExclusiveGateway are the exceptions to this because they can be used to merge parallel flows into one flow.


If you have Gateways, other than ParallelGateways, with less than two outgoing flows, you should revise your design and add more outgoing flows or remove the useless Gateway.