Ping-Yu Hsu Yuan-Bin Chang Yen-Liang Chen STRPN: A Petri-Net Approach for Modeling Spatial-Temporal Relations between Moving Multimedia Objects. 63-76 2003 29 IEEE Trans. Software Eng. 1 http://www.computer.org/tse/ts2003/e0063abs.htm db/journals/tse/tse29.html#HsuCC03