1. A process for modeling a manufacturing plant, which comprises delineating a set of factory operating rules which define how part lots interact with machines in actual operation of the plant, defining the manufacturing plant by specifying machines in the plant and at least batch size and processing time parameters of each machine, defining products manufactured in the plant, providing fabrication sequences consisting of process steps for the products manufactured in the plant, assigning the process steps to the machines, defining at least time and yield characteristics of each process step, identifying which phenomena in the manufacturing plant are stochastic in nature, and assigning distributions and parameters of the distributions to the stochastic phenomena.