Zhijiao Xiao Zhong Ming Jianfei Yin Role-Oriented Workflow Modeling Based on Object Petri Net. 837-843 2008 ICYCS http://dx.doi.org/10.1109/ICYCS.2008.238 conf/icycs/2008 db/conf/icycs/icycs2008.html#XiaoMY08