Developed in 1992 by Theodore J. Williams and the Purdue University Consortium, the Purdue diagram — itself a part of the Purdue Enterprise Reference Architecture (PERA) — was one of the first models used to map data flows in computer-integrated manufacturing (CIM).

By defining six layers that contain both information technology (IT) and operational (OT) technology, along with a demilitarized zone (DMZ) separating them, the Purdue diagram made it easier for companies to understand the relationship between IT and OT technologies and establish effective access controls to limit total risk.

As OT technologies have evolved to include network-enabled functions and outward-facing connections, however, it’s time for companies to prioritize a Purdue update that puts security front and center.