The flow editor offers an intuitive and convenient graphical interface for writing process flows. It supports the definition of process flows in a hierarchical and modular manner in terms of tool-independent process statements as well as explicit tool statements. Chapter 5 discusses the capabilities of the flow editor as well as the highlights of the process flow representation used. Process flow information is interpreted by the run controller , which together with the run data base forms the core components for the management of iterative and parallel split-lot experiments . The run controller takes care of the detection of splits, of scheduling multiple runs in parallel operation on workstation clusters, and offers a number of operation modes to facilitate development and debugging of both processes and simulation tools. The run data base stores and retrieves simulation output data and extracted data of any format, with the PIF format being used as primary exchange format for wafer data.