The default behaviour of BPMN, taking every outgoing sequence flow
(where the condition evaluates to true), is not valid for an exclusive
Hence, this behaviour is overriden and replaced by the correct behavior:
selecting the first sequence flow which condition evaluates to true
(or which hasn't got a condition) and leaving the activity through that
If no sequence flow is selected (ie all conditions evaluate to false),
then the default sequence flow is taken (if defined).