Private Dynamic Epistemic Friendship Logic

Recent works have proposed to model social conceptions of rationality (in contraposition to individual rationality) by means of a logic of community. In [11], the authors have defined a logic of friendship to model social relationship as those contained in social networks. In fact, they have focused on the definition of a Facebook feature named Inbox messages. Following this track, we will extend such a work by introducing in this paper the Private Dynamic Epistemic Friendship Logic (PDEFL) to represent public and private communications among agents, in which the privacy can be established in two ways: either it is defined by the sender of the message or it is defined by the receiver of the message. Furthermore, inspired by the way Facebook users can deal with the privacy of their posted messages in what is known as wall, in PDEFL every agent can delimitate his/her privacy level and determine who can see it: everyone (public), only him/her, only friends and only friends of friends.