School of software Engineering;
Beijing University of Posts and Telecommunications;
Beijing 100876;
China;
Key Laboratory of Trustworthy Distributed Computing and Service;
(BUPT);
Ministry of Education;
Beijing 100876;
China;
The Key Laboratory of Rich-Media Knowledge Organization and Service of Digital Publishing Content;
Institute of Scientific and Technical Information of China;
Beijing 100038;
China;
Insitute of Quantitative Social Science;
Harvard University;
Cambridge;
MA;
USA;
Department of statistics;
Harvard University;
Cambridge;
MA;
USA;