When executing a scope activity that is not composite (e.g. a plain activity with an input output mapping), the engine sets the activity instance id on the execution for that scope but not on the parent execution. However, this is the regular behavior with all other scope activities.

the current behavior has the following problems:

• variable queries need extra logic to assign activity instance IDs to variables that are set on scope executions executing such a leaf, scope activity
• the logic to invoke execution listeners is invoked in between the statements that generate a new activity instance Id and that set the Id on the parent execution; this should not be necessary any longer and the statements to store the activity instance Ids can all be moved to the methods PvmExecutionImpl#enterActivityInstance and #leaveActivityInstance
• GetActivityInstanceCmd and PvmExecutionImpl#getActivityInstanceId and PvmExecutionImpl#getParentActivityInstanceId might need improvement then