This paper describes the development of a prototype object-oriented software system for discrete event simulation and the embedded decision processes of a system being modeled based on previously defined formalism [1] and the Smalltalk programming language. The paper addresses the modular and structured representations of physical and logical entities of a manufacturing system for simulation modeling in the form of reusable software objects. The software takes advantage of the natural link between object-oriented programming and simulation and utilizes inheritance and other features of object-oriented programming to achieve modular yet uniform representation at every level of the model. After giving a brief overview of the object-oriented modeling environment and the relationships between software objects and formalism constructs, a small number of object classes and their operations are summarized. The intelligent entities of the formalism utilize a knowledge-based non-programmed decision mechanism implemented in Smalltalk.