The authors discuss the concept and design criteria for a framework that facilitates the performance assessment of shop-floo control systems. Their basic concept includes a simulation model that emulates the shop floo of a wafer fab, sends information to the control system, and eceives information back from the control system. The shop-floo control system is realized as a separate module that interfaces to the simulator via a data layer that contains the current shop-floo status and the control information generated by the controller. The authors provide detailed information on how the simulation model and shop-floo control system communicate and how each system triggers events in the other system. They show how this framework supports the performance assessment of the shop-floo control system under consideration. They also present a prototype of the framework currently implemented in the course of the SRC/International Sematech FORCe project "Scheduling of Semiconductor Wafer Fabrication Facilities."