Production and representation of computer system simulation models

The problem of the production of computer systems simulation models is dealt with. The software production process is generally carried out without considering the performance aspects of the whole system: performance evaluation is generally made later, once the system has been implemented. In this paper the process of the development of a system simulation model which can be used to discover aspects of system behaviour before the system is completely implemented is investigated. This process starts from the knowledge of the technical specifications of the software system and then, proceeding by levels of abstraction, yields a top-down model specification in terms of resources, resource requests resource activities, etc. J.D. Noe and G.J. Nutt's Evaluation Nets are used for the progressive model development. E-nets provide a formal system representation which can either be supplied to a system for the automatic generation of the simulation code, or used for the straightforward coding of the simulation program in any language.