The paper presents authors’ experience in developing and using archi¬tectural descriptions, following the US DoD Architecture Framework, to the analysis and the design of an Air Situation Simulator (ASS). The publication describes how the use of C4ISR architectures in the definition of requirements and analysis of complex systems provides for a conventional description of the domain and for de¬tailed study of the processes in the investigated system. The steps and stages in the description of operational, systems, and technical views of the simulation system are presented. The requirements for the system’s software development are defined on that basis.