1. Peking University, Key Laboratory of High Confidence Software Technologies (Ministry of Education), School of Electronics Engineering and Computer Science, Beijing, China
2. Macquarie Univerisity, Department of Computing, Macquarie University, Sydney, Australia
3. Key Laboratory of High Confidence Software Technologies (Ministry of Education), School of Electronics Engineering and Computer Science, Peking University, Beijing, China, IP Paris, Telecom SudParis, Evry, France