Formal methods for protocol engineering and distributed systems : FORTE XII/PSTV XIX'99 : IFIP TC6 WG6.1 joint international conference on formal description techniques for distributed systems and communication Protocols (FORTE XII) and protocol specification, testing, and verification (PSTV XIX) : October 5-8, 1999, Beijing, China edited by Jianping Wu, Samuel T. Chanson, Qiang Gao