  The aim of this paper is to investigate the interplay between knowledge
shared by a group of agents and its coalition ability. We investigate this
relation in the standard context of imperfect information concurrent game. We
assume that whenever a set of agents form a coalition to achieve a goal, they
share their knowledge before acting. Based on this assumption, we propose a new
semantics for alternating-time temporal logic with imperfect information and
perfect recall. It turns out that this semantics is sufficient to preserve all
the desirable properties of coalition ability in traditional coalitional
logics. Meanwhile, we investigate how knowledge sharing within a group of
agents contributes to its coalitional ability through the interplay of
epistemic and coalition modalities. This work provides a partial answer to the
question: which kind of group knowledge is required for a group to achieve
their goals in the context of imperfect information.
