There will be many instances where parallel processing is required to be performed, the BPMN notation allows multiple methods of depicting parallel paths.
In these patterns there has to be two or more out going sequence flows for the pattern to be valid for parallel processing.
BPEL comments
1 A <flow> element is created to hold all of the outgoing sequence flows.
2 The ncname of the <flow> attribute is taken from the gateway definition name. "Gateway".name
3 A <sequence> element is created for each outgoing sequence flow. The sequence name is taken from the sequence flow name. Sequence Flow.name. If the sequence is unnamed then an unamed sequence element is created
4 All activities proceeding their respective sequence flow reside completely contained within their respective sequence element and occupy the Target Activity place holder.