CONTINUOUS AND DISCONTINUOUS-CHANGE MODELS: CONCEPTS FOR SIMULATION LANGUAGES.

Abstract

Continuous models, based on ordinary and partial differential equations, are widely used in the simulation of physical processes. Such processes often involve phenomena which are conveniently modelled by discontinuous change processes (switching, limiting etc. ). The basic technique for processing models of this kind on a digital computer is a numerical integration technique which advances the solution of the set of differential equations in a step by step manner. Particular care must be taken when discontinuities are present to ensure that the integration proceeds through the point of discontinuity efficiently and accurately. The use of models of this kind is sufficiently widespread for special simulation languages to be developed to simplify their construction. Simulation languages need to be designed so as to deliver to the modeller accurate numerical solutions of the model equations as simply as possible and also to provide constructs and procedures which facilitate the construction of models and the design of experiments to be performed upon them.