The “iceberg” of manufacturing

Walk into a factory. The visible part is the equipment — robots, conveyors, reactors, packaging lines. That’s roughly Level 0-1-2 of the ISA-95 hierarchy: physical process, instrumentation, basic control. Most factory tours stop there.

The much bigger, invisible part is everything that decides what the factory does, when, with what materials, in what quantity, and how it reports back to the business. That’s Levels 3 and 4 : MES (Manufacturing Execution System) and ERP (Enterprise Resource Planning). The orchestration layer.

ISA-95 is the standard that lets these layers talk to each other despite being made by different vendors over decades.

The 5 levels in plain words

┌────────────────────────────────────────────────────────────────┐
│ Level 4 :  Business Planning & Logistics                       │
│           (ERP : SAP, Oracle, Microsoft Dynamics)              │
│           — "Make 10,000 vaccine doses by Friday"              │
└──────────────────────────────┬─────────────────────────────────┘
                               │  ◀── ISA-95 boundary ──▶
                               │  (Production Schedule, Performance, ...)
┌──────────────────────────────┴─────────────────────────────────┐
│ Level 3 :  Manufacturing Operations Management (MOM)           │
│           (MES : Aveva, Siemens Opcenter, GE Proficy, Rockwell)│
│           — "On Monday at 06:00, start Batch B1234 on Reactor R3"│
└──────────────────────────────┬─────────────────────────────────┘
                               │  ◀── ISA-95 / OPC UA ──▶
┌──────────────────────────────┴─────────────────────────────────┐
│ Level 2 :  Supervisory Control (HMI, SCADA)                    │
│           — Real-time operator view + setpoints                │
└──────────────────────────────┬─────────────────────────────────┘
┌──────────────────────────────┴─────────────────────────────────┐
│ Level 1 :  Basic Control (PLC, DCS, Safety PLC)                │
│           — Control loops, interlocks, sequences                │
└──────────────────────────────┬─────────────────────────────────┘
┌──────────────────────────────┴─────────────────────────────────┐
│ Level 0 :  Physical Process                                    │
│           Sensors, actuators, reactors, conveyors              │
└────────────────────────────────────────────────────────────────┘

The vertical integration at the Level 3 ↔ Level 4 boundary is where ISA-95 lives. It’s the contract that ERPs and MES systems honor when exchanging :

1. Product Definition : recipes, BOMs, formulas (links to ISA-88)
2. Production Capability : what each piece of equipment can do, current availability
3. Production Schedule : the order list ERP sends down to MOM
4. Production Performance : the actuals MOM sends back to ERP

Why MES exists at all (Level 3)

ERP runs on transactional time : daily, hourly. Production lives on operational time : seconds, minutes. The gap is huge.

ERP knows : “We need to ship 1000 units of SKU-42 by Friday.” ERP doesn’t know : “Right now machine M3 just stopped due to a sensor fault, M1 has 240 units staged but the batch on M1 needs to finish before M3 can be reassigned.”

That coordination is Level 3 work — done by humans + MES + Schedulers + Quality systems. ISA-95 formalizes who-talks-to-whom-with-what-data so that the upper levels (ERP) don’t pretend to manage real-time logistics and the lower levels (DCS) don’t pretend to manage business outcomes.

ISA-95 vs Asset Administration Shell (AAS)

The German Plattform Industrie 4.0 has developed the Asset Administration Shell (AAS) as the digital twin standard for Industry 4.0. AAS sits at a similar interface but with a more modern, semantic data model (RDF, ontologies). It’s complementary, not a replacement.

In 2024-2026, ISA-95 v3 work explicitly aligns the B2MML / ISA-95 data structures with AAS so that the two can coexist without translation pain. Practical effect : modern MES implementations support BOTH ISA-95 / B2MML for legacy integration AND AAS submodels for forward-looking digital twin features.

The “Industry 4.0 vendor checklist” with ISA-95 in mind

When evaluating a smart manufacturing initiative or vendor pitch, ISA-95 is a reasonable benchmark :

• Does the proposed solution respect the level hierarchy or does it try to bypass MES and connect ERP directly to PLCs? (Red flag : tight coupling at wrong levels.)
• Does it speak B2MML or a proprietary equivalent ? (Lock-in risk.)
• Does it model the 4 activity categories (Production, Maintenance, Quality, Inventory) explicitly ? (If only Production, it’s incomplete.)
• Does it handle historical data at Level 3 properly (genealogy, batch record reconstruction) ?

These questions reveal whether a vendor truly understands manufacturing operations or just rebadges a generic data lake.