BPMN v2.0, are there rules regarding opening and closing gate?

does somebody know if there are written rules regarding opening and closing gates? Does an opening gate need (closing gate or endEvent)?
in my opinion the enclosed diagram is not executable, but does it meet the specification?18

There is no obligation to add closing gates mirroring opening gates. It is a good practice / modeling guideline though. The example you shared may run in a livelock due to the way you use AND gateways.


one point yet, actually, I like the word mirroring, nevertheless, the enclosed pic should be possible and ‘good’ bpmn-style, shouldn’t it?