Published on in Vol 23, No 1 (2021): January
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/19928, first published
.

1 The Institute of Software, Chinese Academy of Sciences , Beijing , CN
2 Department of Computer Science, University of Toronto , Toronto, ON, CA
3 School of Computer Science and Information Systems, Pace University , New York, NY, US
4 IBM Research , Cambridge, MA, US
5 Zuoshouyisheng Inc , Beijing , CN
*these authors contributed equally