 We saw the example of a completely private announcement in  Figure 3,  a complex action in which one agent learns something without the other agents even suspecting that this is so. Before devising an action model for another similarly complicated action, let us return to our most basic action: the public announcement of p. The idea of this action is that all agents receive the information that p is true, and this is common knowledge. So to construct an action model for this action, we need only one event e that conveys the announcement that p is true, and the occurrence of this event should be common knowledge. This leads us immediately to the action model \(\Pub(p)\) pictured in Figure 4. 