Engineering processes in machine and plant engineering are organized sequentially based on the respective specialist disciplines. To begin with, a new machine or plant is designed mechanically. This is followed by electrical construction and then software development (steps that are neglected in this simplified representation include, e.g. hydraulic construction, technical documentation, etc.):
Only once a sensor/actuator list has been set during mechanical construction can the assignment of inputs and outputs for hardware construction begin. Software developers begin programming as soon as a finished schematic with IO assignments becomes available.