  As demonstrated in many recent studies, cooperation between users can greatly
improve the performance of communication systems. Most of the works in the
literature present models where all the users are aware of the resources
available for cooperation. However, the scenario where cooperation links are
sometimes unavailable or that some users cannot be updated whether the
cooperation links are present or not, is more realistic in today's dynamic
ad-hoc communication systems. In such a case we need coding schemes that
exploit the cooperation links if they are present, and can still operate if
cooperation is not possible. In this work we study the general broadcast
channel model with degraded message sets and cooperation links that may be
absent, and derive it's capacity region under such uncertainty conditions.
