The evolution of Information Technology leads company functions towards greater integration. A lot is being said currently about ERP (Enterprise Resource Planning) systems: products that provide decision-making supports for planning, depending on the resources available.
These systems have undergone an evolution that has brought less expensive and more open software packages onto the market, intended for a vast user area. Feeding these systems is the true critical point: manual input of the data relative to the production flow runs the risk of putting the actual efficiency of complex and costly optimisation algorithms into doubt.
The traditional architecture that fed these systems with dedicated networks consisting of swarms of little terminals, most of them fitted with a barcode reader, no longer fully satisfies the requirements of ERP systems. Today the end user finds himself in the condition of already having interface PCs in the field.
Thus the question: "Seeing that the production data are already in a PC, why not take them directly from there automatically and pass them on to the management systems?".
The world of ERP systems and the HMI (human-machine interface) one remain, however, culturally very far apart. A determining role for the union of the two worlds is played by EPS (Enterprise Production Systems) applications. EPS is a new term, more probing and exhaustive than the old, and less appropriate, term MES (Manufacturing Execution System).
EPS is a term coined by ARC Advisory Group Inc.

The diagram shows the architecture of industrial information systems.
Two macro-levels are highlighted: Management and Plant. Management is further divided into ERP and EPS for, respectively, the planning function and programming the activities.
Plant consists of the HMI layer, namely the machine (or plant) operating level, while the PBC (PLC-PC Based Control) layer is reserved for the part dedicated to process control. The suggested division highlights the connection points while keeping the functions of each level well apart.