The §loop project, launched in 1995, works on three main domains: (1) discrete event simulation, (2) parallel object-oriented languages and (3) interconnection networks. One of the research objective of the project is the development of {\sc Prosit}, a sequential and distributed object-oriented workbench for discrete event simulation. Object orientation is used to ensure two main concerns: \begin{itemize} \item performance on conventional, networked and multi-processor machines \item versatility and ease of use. \end{itemize} We have now achieved the first part of {\sc Prosit}. We have completely specified the simulation and the execution models, and we have a sequential C++ version of the simulator. This report concentrates on the modelling process and the object oriented architecture of the sequential simulator. As an illustration of possible applications, we present the classes supporting the queueing network paradigm.