Published on in Vol 7 , No 2 (2020) :Jul-Dec
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/18589, first published
.

1 School of Mathematical and Computer Sciences, Heriot-Watt University, Edinburgh, GB
2 School of Computing and Communications, The Open University, Milton Keynes, GB
3 Knowledge Media Institute, The Open University, Milton Keynes, GB
4 PJ Care Limited, Peterborough, GB