Abstract
The proposals discussed in the paper are used for the development of a system providing assistance to the security staff during a large-scale event involving a large number of participants. A subsystem deals with the SMS messages sent by the security staff (observers) and processes the information they convey. The system provides the security personnel (analysts) with visualization facilities and suggestions for actions, and keeps track of the information exchanged for further use. The paper presents arguments in favor of the formalism called XRCDC (an extension of the Region Cardinal Direction Calculus) designed to represent events and spatiotemporal reasoning about them.