The possibility of including real PLCs in CAPE tools has been around since the mid 90s, utilizing vendor-specific protocols. Some common purposes are offline programming, verification, and optimization. Since the beginning of the last decade, many CAPE tools have an OPC client implemented, usually an OPC DA client, which makes it possible to connect to any OPC DA server [38]. The I/Os in the PLC control code are made available to the OPC server. CAPE tools usually have some kind of signal representation similar to real machines, e.g., a start signal for a robot. These signals are then mapped to the I/Os from the PLC via OPC. The simulated machine or process can thereby be controlled in the same way as it would be in reality. Examples of CAPE software with OPC functionality include: Delmia Automation, Visual Components, Process Simulate, and Arena.