Glossary · MES and ISA-95
ISA-95 hierarchy
Also known as: Automation pyramid, Purdue model levels, ISA-95 levels
German: ISA-95-Hierarchie
In ISA-95 / IEC 62264, the functional hierarchy divides manufacturing functions into levels: Level 0 the physical process, Level 1 sensing and manipulating, Level 2 monitoring and supervisory control, Level 3 manufacturing operations management and Level 4 business planning and logistics.
- MES
- Standards
In one sentence
The ISA-95 hierarchy divides manufacturing functions into Levels 0 to 4, from the physical process up to business planning and logistics.
Example
The architecture diagram places sensors and drives at Levels 0 and 1, PLCs and SCADA at Level 2, the MES at Level 3 and the ERP at Level 4.
How it applies
- Engineering: The levels help assign functions to systems and define interfaces; ISA-95 itself focuses on the interface between Levels 3 and 4.
- Security: Network architectures often use the levels to structure zones, following the Purdue reference model; IEC 62443 then defines zones and conduits based on risk.
- Time frames: Higher levels work in longer time frames (months to days at Level 4, days to seconds at Level 3), lower levels in seconds and below.
- Documentation: System overviews and architecture diagrams become easier to read when they use the level numbers consistently. The documentation team should state which level a described system belongs to and which interfaces cross levels.
ISA-95 hierarchy vs. automation pyramid
The automation pyramid is an informal picture of the same idea. With cloud services and edge devices, real systems often cut across levels; the ISA-95 levels still describe functions, not physical devices.