Hi Yi,
jBPM-4.4 just achieve some features of BPMN 2, this work didn't complete yet. please refer this post for more information.
http://community.jboss.org/thread/154623?tstart=0
https://jira.jboss.org/browse/JBPM-2926
If you have any ideas about it, please tell us. Thank you very much.