What is ISA-95?
ISA-95 is the Enterprise-Control System Integration series of standards from the International Society of Automation (ISA), adopted internationally as IEC 62264, which uses shared models, objects and terminology to define how business systems such as ERP and production systems such as MES, SCADA and DCS exchange information. The standard does not tell you how to automate a plant; it tells you which functions belong at which level and which data crosses the boundary between the office and the shop floor. That makes ISA-95 one of the most important foundations for structurally linking IT and OT systems.
ISA-95 = the bridge between ERP and the factory floor.
The aim is to prevent confusion, duplicated work and integration issues in automation projects in production environments.
🧠 Why was ISA-95 created?
Without a shared structure, IT and OT often talk past each other:
- ERP thinks in orders and quantities - “produce 20,000 bottles of item X next week”.
- OT systems think in machines, batches and processes - which line, which recipe, which operator, which raw material lot.
- Every interface became custom work - with its own terms, its own data models and therefore high costs with every change.
In the mid-1990s the ISA therefore set up the ISA95 committee. It built on the Purdue Reference Model for Computer Integrated Manufacturing, developed with Theodore Williams of Purdue University, who was himself one of the early committee members. Part 1 was published in 2000 as ANSI/ISA-95.00.01-2000, Part 2 in 2001 and Part 3 in 2005. The most recent revision of Part 1 (ANSI/ISA-95.00.01-2025) appeared on 10 April 2025 and mainly clarifies the boundary between the enterprise domain and the manufacturing and control domain.
📚 Which parts make up ISA-95?
ISA-95 has eight parts. Parts 1 to 3 are aligned with the international IEC 62264 series, which is why the ISA versions carry the label “IEC 62264 Mod”.
| Part | Title | Current ISA edition | Content in brief |
|---|---|---|---|
| 1 | Models and Terminology | 2025 | Levels, equipment hierarchy, functional data flow model, terms |
| 2 | Objects and Attributes for Enterprise-Control System Integration | 2018 | Objects and attributes for the exchange between levels 3 and 4 |
| 3 | Activity Models of Manufacturing Operations Management | 2013 | Activities within level 3 (production, maintenance, quality, inventory) |
| 4 | Objects and Attributes for Manufacturing Operations Management Integration | 2018 | Objects for the exchange between activities within level 3 |
| 5 | Business-to-Manufacturing Transactions | 2018 | Transactions and message structures between business and production |
| 6 | Messaging Service Model | 2014 | How messages are delivered between applications |
| 7 | Alias Service Model | 2017 | Translating different identifiers for the same object |
| 8 | Information Exchange Profiles | 2020 | Reusable profiles for concrete information exchanges |
At IEC, editions include IEC 62264-1:2013 and IEC 62264-3:2016, each a second edition. In Europe they have been adopted as EN 62264.
🧭 Which levels does ISA-95 define?
The functional hierarchy model in Part 1 has five levels. Each level works on its own time scale: the standard states it explicitly for levels 4 and 3, while for the control levels it speaks of sub-second response times.
| Level | ISA-95 name | Time scale | Typical systems |
|---|---|---|---|
| 4 | Business planning and logistics | Months, weeks, days | ERP, supply chain management |
| 3 | Manufacturing operations management (MOM) | Days, shifts, hours, minutes, seconds | MES, MOMS, LIMS, CMMS, historian |
| 2 | Monitoring, supervisory and automated control | Real time, sub-second response | PLC, DCS, SCADA, HMI |
| 1 | Sensing and manipulating the process | Real time, together with level 2 | Sensors, actuators, valves |
| 0 | The physical production process | Continuous | Reactors, conveyors, machines |
Even the meaning of “real time” differs per level. For a level 3 system it means information is available a few seconds after an event on the shop floor; for level 4 it means logistics and material data are updated daily. Connecting ERP directly to machine signals ignores that difference and produces a data stream ERP cannot handle.
Note two differences from the Purdue Model as used in security architectures. There, the PLC sits on level 1 as basic control and SCADA on level 2, whereas ISA-95 places all automated control on level 2. The Purdue model also has a level 5 (enterprise network), which lies outside ISA-95. Moreover, the core of ISA-95 is not the whole pyramid but the boundary between level 3 and level 4.
Figure: the five functional levels of ISA-95, with the boundary between MES and ERP as the core of the standard.
🏭 What does the equipment hierarchy look like?
Besides the functional levels, Part 1 defines a role-based equipment hierarchy. It gives every installation a fixed place, so that ERP and MES mean the same thing by “line 3”:
| Level | Description | Example |
|---|---|---|
| Enterprise | The company as a whole | A dairy group |
| Site | A plant or premises | A production site in Leeuwarden |
| Area | Physical, geographical or logical grouping within the site | Filling |
| Work center | Unit scheduled by level 4 or 3: process cell, production unit, production line or storage zone | Filling line 3 |
| Work unit | Lowest element scheduled by level 3: unit, work cell or storage unit | Filler, labeller |
The terms process cell and unit come straight from ISA-88, the batch control standard, so the two standards fit together seamlessly. In a Unified Namespace the same hierarchy is often used as the topic structure, for example enterprise/site/area/line/cell.
🔧 What do the object and activity models describe?
Object models (Parts 2 and 4) define which information is exchanged. The four basic resources are personnel, equipment, physical assets and material. On top of these sit process segments, product definitions, production capability, production schedules and production performance, among others. A production order from ERP thus becomes a production schedule, and the feedback from MES a production performance. Later editions generalise these objects to operations schedule and operations performance, so the same structure also works for maintenance, quality and inventory orders.
Activity models (Part 3) divide level 3 into four categories:
- Production operations management - the actual production
- Maintenance operations management - maintenance of equipment, often through a CMMS
- Quality operations management - testing and release, often in a LIMS or QMS
- Inventory operations management - storage and internal movement of material
Within each category Part 3 uses the same generic activity model: resource management, definition management, detailed scheduling, dispatching, execution management, data collection, tracking and performance analysis. Tracking forms the basis for tracking and tracing and batch and lot genealogy; performance analysis feeds KPIs such as OEE.
🔗 How is ISA-95 applied technically?
ISA-95 itself is a model, not a protocol. The translation into technology happens through derived specifications:
- B2MML - the XML implementation of ISA-95 by MESA International. Version V0700 was released in March 2021, supports the 2018/2019 editions of ISA-95 and IEC 62264, and for the first time also includes a JSON schema. It is free to use, with attribution to MESA.
- OPC UA for ISA-95 - the companion specification OPC 10030 (ISA-95 Common Object Model, version 1.00 from October 2013) models personnel, equipment, physical assets and material in OPC UA. OPC 10031-4 (Job Control, version 1.00 in 2021, version 2.00 in January 2024) describes how MES sends jobs to machines and reads back the results.
- MQTT and Unified Namespace - not part of ISA-95, but in practice many topic structures follow the ISA-95 equipment hierarchy.
🔁 How does ISA-95 relate to ISA-88, Purdue and IEC 62443?
| Standard or model | Focus | Relationship to ISA-95 |
|---|---|---|
| ISA-88 | Batch control, recipes and procedural control | Supplies the terms process cell and unit; recipe management at levels 2 and 3 connects to product definitions in ISA-95 |
| Purdue Model | Reference model from process to enterprise | Source of the ISA-95 levels; security models use a slightly different split |
| IEC 62443 | Cybersecurity of industrial systems | Uses the levels as a starting point for zones and conduits |
| PackML | Machine states in packaging lines | Delivers standardised machine data from level 2 to level 3 |
🔐 What does ISA-95 mean for OT security?
ISA-95 is not a security standard, but the boundary between levels 3 and 4 is in practice exactly where IT and OT meet. That is where you place an IDMZ, so that ERP never talks directly to MES or control systems. Because ISA-95 defines the messages exchanged, you can specify precisely in the firewall and in the conduit between the zones which flows are permitted. For organisations within the scope of NIS2 and the Dutch Cybersecurity Act (Cyberbeveiligingswet), this split is a logical starting point for network segmentation and for the zones and conduits model of IEC 62443.
🏭 What does an ISA-95 integration look like in practice?
Take the filling line of the dairy group from the example above. An order then passes through this chain:
- ERP plans an order for 20,000 bottles next week and sends it to MES as a schedule, for example as a B2MML message.
- MES creates a detailed schedule, selects filling line 3 and dispatches jobs to the filler and labeller.
- The PLCs and SCADA execute and report counts, stoppages and consumed raw material lots to MES.
- MES reports back to ERP with a performance message: quantity produced, consumption per lot and quality status.
- ERP books stock and costs without ever having communicated with a machine.
| Aspect | Without ISA-95 | With ISA-95 |
|---|---|---|
| Interfaces | Every link between ERP and production is custom-made | Standardised messages and objects, reusable per line and site |
| Terminology | Duplicate data models and inconsistent terms | One equipment hierarchy and shared terms |
| Feedback | ERP does not know exactly when production is finished or has stopped | MES reports progress, consumption and downtime in a structured way |
| Orders | Re-keyed by hand or passed on in spreadsheets | MES receives orders as standardised production instructions |
| Changes | Replacing one system affects every interface | Systems can be replaced as long as the interface stays the same |
🧭 How do you apply ISA-95 step by step?
- Map the equipment hierarchy - from enterprise to work unit, with unambiguous names shared by ERP, MES and SCADA.
- Set the system boundaries - which function belongs in ERP (level 4) and which in MES (level 3)? Think of detailed scheduling, recipes and quality release.
- Define the information flows - orders going down, progress, consumption and quality results going up, using the objects from Part 2.
- Choose an implementation format - B2MML for message exchange, OPC UA for machine connections or a Unified Namespace as the central data layer.
- Design the secure connection - an IDMZ on the boundary between levels 3 and 4, carrying only the defined flows.
- Start with one line - validate the models on a single brownfield line before rolling out across multiple sites.
❓ Frequently asked questions
Is ISA-95 the same as IEC 62264?
ISA-95 and IEC 62264 describe essentially the same models. ISA-95 is the American ANSI/ISA standard; IEC 62264 is the international version based on it. The ISA versions of Parts 1 to 3 are labelled “IEC 62264 Mod”.
Is ISA-95 a software product or a protocol?
ISA-95 is neither software nor a communication protocol, but a set of models and terms. Implementations such as B2MML and the OPC UA companion specifications for ISA-95 make the models technically usable. MES and ERP vendors often build their interfaces on those specifications.
Which levels does ISA-95 cover?
ISA-95 describes levels 0 to 4, from the physical process up to business planning and logistics. The standard focuses mainly on the interface between level 3 (manufacturing operations management) and level 4 (ERP). Level 5 of the Purdue model lies outside ISA-95.
What is the difference between ISA-95 and ISA-88?
ISA-95 governs the integration between business systems and production, with the emphasis on levels 3 and 4. ISA-88 standardises batch control, recipes and procedures within production. Both use the same equipment terms, such as process cell and unit, so they complement each other.
What is B2MML?
B2MML (Business To Manufacturing Markup Language) is the freely usable XML implementation of ISA-95, published by MESA International. Since version V0700 from 2021 there is also a JSON schema. B2MML is used to exchange production orders, production feedback and master data between ERP and MES.
Do I need ISA-95 for an MES project?
ISA-95 is not mandatory, but almost every MES project uses its terms and levels. By describing functions and information flows according to ISA-95, you can compare vendors more consistently and avoid custom interfaces. That lowers the cost of later extensions or system replacements.
📌 In summary
ISA-95 provides a framework for connecting ERP, MES and production automation. With five functional levels, a role-based equipment hierarchy, object models and activity models, ISA-95 (IEC 62264) makes communication between IT and OT systems consistent, scalable and understandable. Through B2MML, OPC UA and the Unified Namespace it is a practical foundation for Smart Industry and IT OT convergence.