The Four Layers Under MES, Top Down

Last month I wrote that AI is architecture, not a feature, and showed you the project at the relational core. Several of you wrote back asking the next question.
What is actually inside the database, and how do the layers connect?
Top down, four of them. The rest of this article walks them in order.
Building AI Infrastructure for an Engineering Firm: The Complete Data Architecture

AI infrastructure for engineering firms requires a connected data layer linking all five core departments, Operations, Accounting, HR, Sales, and Marketing, so information flows automatically without manual handoffs between systems.