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  • Writer's pictureMatthew Barber

What is the ISA-95 model, and where does MES fit?

ISA-95 Model

The ISA-95 model, also known as ANSI/ISA-95 or ISA-95, is a global standard for enterprise and control system integration. The model is designed to provide a consistent framework for integrating business and manufacturing processes, enabling seamless information exchange between enterprise and control systems on the shopfloor.

ISA-95 is widely recognised and accepted as the de-facto standard for manufacturing system integration and is used by many companies around the world.

The model is developed and maintained by the International Society of Automation (ISA), a non-profit organisation that sets standards for industrial automation and control systems. The model was first published in 1995.

It consists of five levels, each representing a different layer of the manufacturing system. These levels are:

  • Level 0 - Physical equipment layer such as the machines on the shopfloor.

  • Level 1 - Physical sensors on the equipment, such as PLCs to monitor processes.

  • Level 2 - Monitoring and supervising layer, such as the logic in PLCs to control and monitor the process.

  • Level 3 - Manufacturing operations management layer, managed by an MES application.

  • Level 4 - Enterprise business systems layer, managed by ERP.

All of these layers communicate, allowing data to flow between the different systems in the factory.

This model is often depicted as a pyramid. For the purposes of MES we can consolidate levels 0, 1, and 2 together and consider them to be an output that MES can connect to in order to take real-time readings about the production process.

Communication between systems

Data flows from ERP to MES, information like the production order schedule and shared master data is sent to MES. MES then takes over and manages the factory operations, reporting key data back to ERP to keep the systems aligned. MES typically sends a subset of aggregated data back, it's not good practice to keep masses of detailed data in ERP, when MES is better suited to store, organise, and report on that information. ERP needs to know about anything related to costs, production volumes, order fulfilment, and inventory.

MES reads data directly from the OPC/PLC layer, typically through an OPC server. Other communication protocols such as MTConnect can also be used to collect data. PLCs not only read data about the process, but they can also control the process. MES can send instructions via OPC to control the process, such as starting/stopping production orders, or setting machine set points, removing the need for the operators to define the set points manually.

Deeper Dive into the ISA-95 layers

The physical equipment layer (Level 0) represents the manufacturing process, including the machines and other equipment in the production line. Physical sensors (Level 1) monitor the physical equipment layer, reading information about the process in real-time such as counts, machine stops, and process variables such as temperatures and speeds.

The monitoring and supervising layer (Level 2) includes the control systems that operate and monitor the physical equipment, typically implemented on programmable logic controllers (PLCs) which are small high-speed computers used to read sensor data and perform logic. PLCs are programmed in "ladder logic" which are programs graphically coded in a similar way to an electrical wiring diagram. This layer could involve distributed control systems (DCS), and supervisory control and data acquisition (SCADA) systems.

The manufacturing operations management layer (Level 3) includes the software systems that manage the manufacturing process, such as manufacturing execution systems (MES). If an MES isn't in place, then a collection of other applications could fill this space, such as:

  • Quality Management Systems (QMS).

  • Computerised Maintenance Management Systems (CMMS).

  • Enterprise Asset Management (EAM) systems.

  • Warehouse Management System (WMS).

Depending on the scope of the MES system, some of these applications may exist alongside an MES system. It's important to consider the full breadth of the MES system during the buying cycle, as some MES systems could lack some of this functionality. Even if you don't require the functionality up front, it's important to future-proof, so it's easier to expand the scope of the MES going forward.

This layer is responsible for coordinating the activities of the control layer to optimise the manufacturing process.

The business planning and logistics layer (Level 4) includes the software systems that manage the planning and logistics of the manufacturing process, such as:

  1. Enterprise Resource Planning (ERP) systems for finances, supply chain, and human resources.

  2. Supply Chain Management (SCM) systems.

  3. Customer relationship management systems.

This layer is responsible for coordinating the manufacturing process with the overall business objectives.

The ISA-95 model provides a standardised framework for integrating these different layers of the manufacturing system, enabling seamless information exchange between the different systems. This integration allows for real-time visibility into the manufacturing process, which can help to identify and resolve issues quickly, reduce downtime, and optimise the manufacturing process.


One of the key benefits of the ISA-95 model is that it provides a standardised language for communication between different systems. This common language makes it easier for different systems to communicate with each other, reducing the risk of miscommunication and errors.

The model provides a standardised framework for data exchange. This framework makes it easier to exchange data between different systems, reducing the need for manual data entry and improving data accuracy.


The ISA-95 model is a widely recognised and accepted standard for integrating business and manufacturing processes. By providing a standardised framework for integrating different layers of the manufacturing system, the ISA-95 model enables seamless information exchange between different systems. This integration can help to improve the efficiency and effectiveness of the manufacturing process, reducing downtime, and improving overall business performance.

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