A Manufacturing Execution System (MES) is a level of a multi-layer production management system that operates in close proximity to the process. The German term "Produktionsleitsystem" is often used as a synonym. Compared to similarly effective systems for production planning, so-called ERP systems (Enterprise Resource Planning), the MES is characterised by the direct connection to the distributed systems of process automation and enables the management, guidance, control or monitoring of production in real time. This includes classic data collection and processing, such as production data acquisition (PDA), machine data acquisition (MDC) and personnel data acquisition, but also all other processes that have a timely effect on the manufacturing/production process.