  Though a lot of work in multi-agent systems is focused on reasoning about
knowledge and beliefs of artificial agents, an explicit representation and
reasoning about the presence/absence of agents, especially in the scenarios
where agents may be unaware of other agents joining in or going offline in a
multi-agent system, leading to partial knowledge/asymmetric knowledge of the
agents is mostly overlooked by the MAS community. Such scenarios lay the
foundations of cases where an agent can influence other agents' mental states
by (mis)informing them about the presence/absence of collaborators or
adversaries. In this paper, we investigate how Kripke structure-based epistemic
models can be extended to express the above notion based on an agent's
subjective knowledge and we discuss the challenges that come along.
