The simplest informational event is one where indubitable information becomes available through a public announcement or a public observation. Technically, this reduces the current range of options that agents need to take into account in a manner that is transparent to all. The resulting system of public announcement logic is the simplest system of information flow, and it has become a pilot for subsequent work in dynamic-epistemic logic.

In terms of information, the structures used here are models for epistemic logic interpreted as giving the semantic information of agents. One may see this as a first approximation to the knowledge that agents can be said to have, though much more sophisticated analyses exist for knowledge in its ordinary and philosophical uses.