"Purdue Model" is the short name for the Purdue Reference Model for Computer Integrated Manufacturing (ISA Publication). This is a reference model for enterprise architecture developed in the early 1990s by Theodore J. Williams and members of the Industry-Purdue University Consortium for Computer Integrated Manufacturing. It provides a framework for modeling people, facilities and systems in multiple architectural levels and through all phases of the enterprise life cycle.

ISA initially published this in 1989, and although it was reprinted in 1991, it has received only minor editorial corrections since then. Many Owner/Operators, EPCs, and vendors have used it, usually developing confidential versions for their internal use. When the book went out of print, ISA agreed to make it freely available on the PERA website

Key Components of the PERA Model include:

1. Enterprise Life-cycle Framework: This life-cycle helps in planning, designing, implementing, and maintaining enterprise systems.
2. Levels of Automation: PERA defines Control and Information System levels from control and interlocking of physical equipment to business systems.
3. Physical and Logical Architectures: It divides enterprise systems into physical and logical architectures.
4. Reference Data Flow Models: Example reference data flow models for a generic industry.
5. Concepts of maximum and minimum lines of automation as applied to both Control and Information Systems, and Manufacturing Facilities.

Typical Levels of the Purdue Model
Although 5 levels is most common, larger corporations or consortiums may define more.

The Purdue Model is widely used in industrial control systems (ICS) and cybersecurity to segment and secure networks. It helps in creating a defensible environment by segmenting industrial control system networks from corporate enterprise networks and the internet. Sometimes additional "DMZ zones" may be identified such as Level 3.5 for plant/office "firewalls".