In contrast with classical simulation languages, the present trends are evolving towards fully integrated interactive modelling and simulation evironmens. These environments have to combine interdisciplianry tecniques such as expert systems, object oriented programming and data base management.To achieve the above objectives, the architecture of the simulation programming language and that of the run-time simulation environment which exercises the models should be deinged allowing modularity and flexibility. Furthermore, the robustness of the environment should be reinforced. In this paper the MUSS simulation system is presented, emphasizing the innovative conepts: the hierachcical architecture of the MUSS simulation language, the preprocessor analysis anf segmentation pases and the structure of the run-time simulation environment.