  Many application domains require representing interrelated real-world
activities and/or evolving physical phenomena. In the crisis response domain,
for instance, one may be interested in representing the state of the unfolding
crisis (e.g., forest fire), the progress of the response activities such as
evacuation and traffic control, and the state of the crisis site(s). Such a
situation representation can then be used to support a multitude of
applications including situation monitoring, analysis, and planning. In this
paper, we make a case for an event based representation of situations where
events are defined to be domain-specific significant occurrences in space and
time. We argue that events offer a unifying and powerful abstraction to
building situational awareness applications. We identify challenges in building
an Event Management System (EMS) for which traditional data and knowledge
management systems prove to be limited and suggest possible directions and
technologies to address the challenges.
