Digital transformation and global society 4th International Conference, DTGS 2019, St. Petersburg, Russia, June 19-21, 2019 : revised selected papers - Aleksandrov, Daniel A.; Bychanovskij, Aleksandr Valerʹevič 19XX-; Chugunov, Andrei V.; Kabanov, Jurij; Kolʹcova, Olesʹja; Musabirov, Ilya (Communications in computer and information science, 2019)