Yuyue Du Shandong 1982, his received his BS degree from University, Jinan, China in MS degree from Nanjing University of Aeronautics and Astronautics, Nanjing, China in 1991, and his PhD degree in computer applications from Tongji University, Shanghai, China in 2003. He is currently a profes- sor in the College of Information Sci-ence and Engineering, Shandong University of Science and Technology, Qingdao, China. He is a member of the Professional Committee of Petri Nets of the China Computer Federation. His research interests are in formal engineering, Petri nets, real-time systems, Web services, and workflows. He has taken in over ten projects sup- ported by the National Natural Science Foundation of China, Na- tional Key Basic Research Developing Program of China, and other important and key projects at provincial levels. He has published more than 140 papers in domestic and international academic publications, with more than 80 SCI and EI citations, and a total of more than 270 citations. Yuhui Ning received his BSc degree and MSc degree in computer science and technology from Shandong University of Science and Technology, Qingdao, China in 2005 and 2008, respectively. He is currently a PhD candi- date in computer software and theory in the College of Information Science and Engineering, Shandong University of Science and technology, Qingdao, China. His research interests include Petri nets, Web services, and workflow theory.E-mail: ningyuhui@ 163.com