1. School of Software Technology, Dalian University of Technology, Dalian 116620, China, and Key Laboratory for Ubiquitous Network and Service Software of Liaoning Province, Dalian 116620, China gaojing@dlut.edu.cn
2. School of Software Technology, Dalian University of Technology, Dalian 116620, China lipeng2015@mail.dlut.edu.cn
3. School of Software Technology, Dalian University of Technology, Dalian 116620, China, and Key Laboratory for Ubiquitous Network and Service Software of Liaoning Province, Dalian 116620, China zkchen@dlut.edu.cn
4. School of Software Technology, Dalian University of Technology, Dalian 116620, China zhang1234567893@mail.dlut.edu.cn