 Private information. Private information is an equally important aspect of our social interaction. Consider scenarios where the announcing agent is aware of the private communication whilst other members of the group are not, such as emails in Bcc. Consider also scenarios where the sending agent is not aware of the private communication, such as a surveillance operation. The system of dynamic epistemic logic (DEL) models events that turn on private (and public) information by modelling the agents’ information concerning the events taking place in a given communicative scenario (see Baltag et al. 2008; van Ditmarsh et al. 2008; and Pacuit 2011). For an excellent overview and integration of all of the issues above, see the recent work of van Benthem (2016), where the author discusses multiple interrelated levels of logical dynamics, one level of update, and another of representation. For an extensive collection of papers extending this and related approaches, see Baltag and Smets (2014)