Does BPMN layouting for pool work only on top level?

Question

When using pools on top level of your graph, the nodes are correctly connected to the correct lane and BPMN layout also works.

But if you have the same pool in the subprocess activity graph, the BPMN layout does not work. It seems that the activities are not connected to the cells anymore.

 

Example:
https://www.dropbox.com/s/7qbem9tsqg2x8gf/test.graphml
* The first graph is OK
* The graph of task4 is not OK (although this is the exact copy of first graph).

Answer 1

Yes, BPMN pools are only supported on top level. If you use a pool node inside a subprocess, the pool node is treated like a normal group node (meaning its rows and columns are ignored).

Comments

Why?

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Because a) the BPMN specification does not account for nested pools and b) there is no layout algorithm in the world that can handle the general case of nested pools.