Graphical programming of simulation models in an object-oriented environment

Abstract

Graphical programming, which is used here to mean creation of simulation models graphically, has been used in conjunction with conventional simulation languages via block diagrams or activity networks. Its beneficial effects on model development in simulation have been generally accepted. However, none of these conventional simulation languages has reached a level of graphical programming that would impact the user's programming task substantially. Today, this is possible with the current software and hardware technology. An interactive incremental programming environment supported by a good graphical programming system that helps automatic model development, specification and verification would be greatly appreciated in modeling in general, but especially in simulation of complex real-life systems. Such a visual system could essentially be a conceptual framework for analysis of the problem at hand and become a means of communication among the people who are involved in development and management of systems. It can also be the friendly interface that forms a communication medium between the modeler and the computer for automatic programming. In this research paper, a prototype graphical programming methodology for modeling and automatic interpretation of simulation problems is developed in the object-oriented environment of the Smalltalk-80 language. The modeler uses a high-level graphical representation formalism based on the activity-cycle diagrams to define simulation models in an interactive mode. These activity-cycle diagrams can then be interpreted into the underlying program ming language and executed automatically. Thus, the modeler does not have to know the underlying Smalltalk 80 language in order to use our prototype simulation system. The future expansions to this system will include a simulation object editor, a graphical output view system and a richer high-level concept base for modeling purpose.