Structure notation of dynamic systems: A pictorial language approach

This paper describes a visual programming environment called PROX (Pictorial Programming for Control Systems and Simulation) and its application to the development of software code for dynamic systems. We show how PROX is used for modeling and simulating a continuous process of interdependent variables with emphasis on user software development. Some of PROX key features are highlighted, such as encouraging users to consider the structure of the model and the interdependency of variables through feedback processes as the cause for behaviour in dynamic systems. PROX is an example of how Software Engineering (SE), Artificial Intelligence (AI) and model building can be integrated into a single framework to help users to generate code and create their own understanding of dynamic systems. PROX is written in Pop-11 under X-Windows allowing the user to write application programs by simply connecting icons. As the building blocks are hooked together, PROX creates equations and procedures behind the scenes and, as soon as the connections are drawn, programs can be run immediately and variables can be plotted. In this way, assumptions about the structure of the system being modeled can rapidly be tested without the need for extensive recompilation.