1.1 Digital Systems Landscape Map & Data Ownership

A manufacturing floor running on undefined system boundaries is a guarantee of data corruption. When the ERP tries to read millisecond sensor data, or the PLC attempts to query financial ledgers, the "Single Source of Truth" disintegrates. This results in phantom inventory, untraceable quality escapes, and network storms. You must strictly define the architectural layers (ISA-95) based on Time Horizon and Data Granularity. If a system is not the authorized master of a data point, it must strictly consume that data, never modify it.

The 5-Level Functional Hierarchy

Organize your digital stack into five distinct levels. Data must flow vertically through these layers; skipping levels (e.g., connecting a Sensor directly to ERP) creates unmanageable dependencies and security holes.

Level 4: Business Planning (ERP / PLM)

• Time Horizon: Months to Days.
• Unit of Measure: Dollars ($) and Aggregated Units.
• Role: The ERP (Enterprise Resource Planning) owns the "Business Promise." It manages the general ledger, sales orders, and material requirements planning (MRP). The PLM (Product Lifecycle Management) sits here as the master of engineering definition.
• Constraint: Level 4 systems are transactional. They are too slow for real-time control. Never let an ERP dictate the "Start" or "Stop" of a physical machine directly.

Level 3: Manufacturing Operations (MES / QMS / WMS)

• Time Horizon: Shifts, Hours, Minutes.
• Unit of Measure: Serial Numbers, Lots, Pallets.
• Role: The MES (Manufacturing Execution System) is the "Factory OS." It translates the business plan (L4) into executable work. It owns the immediate state of Work-in-Progress (WIP), enforcing quality gates and tracking genealogy.
• Constraint: Level 3 is event-driven. It responds to operator scans or machine signals. It buffers the high-speed noise of the shop floor before reporting "clean" data back to Level 4.

Level 2: Supervisory Control (SCADA)

• Time Horizon: Seconds to Sub-seconds.
• Unit of Measure: Tag Values, Setpoints, Alarms.
• Role: SCADA (Supervisory Control and Data Acquisition) aggregates data from multiple machines to provide a real-time visualization of the line. It handles recipe management and equipment state monitoring.
• Constraint: Level 2 is supervisory. It does not execute the safety logic; it monitors the controllers that do.

Level 1: Machine Control (PLC / Edge)

• Time Horizon: Milliseconds.
• Unit of Measure: Signals (I/O), Logic States (True/False).
• Role: PLCs (Programmable Logic Controllers) and Edge devices execute the physical logic. They read inputs and drive outputs deterministically.
• Constraint: Level 1 is critical real-time. Any latency here results in physical damage or defects.

Level 0: Physical Process (Sensors / Actuators)

• Time Horizon: Physics (Continuous).
• Unit of Measure: Volts, Amps, Pressure, Temperature.
• Role: The actual hardware doing the work—motors, heaters, conveyors, and sensors.
• Constraint: These devices have no "intelligence" regarding the product identity; they only know their physical state.

Architectural Boundaries & Ownership Rules

Assign system ownership based on the hierarchy level to prevent data conflicts.

Financials & Demand (Level 4)

• Owner: ERP
• Rule: The ERP sets the target (Quantity & Date). MES executes against this target but never changes the original demand record.

Product Specs (Level 4)

• Owner: PLM
• Rule: Engineering specs (BOM, CAD) flow from PLM -> ERP -> MES. Never create a "rogue revision" directly in the MES.

WIP & Traceability (Level 3)

• Owner: MES
• Rule: The MES is the only system that knows the exact location of a specific serial number. ERP only sees the aggregate "WIP Value."

Machine Data (Level 1-2)

• Owner: PLC/SCADA
• Rule: The PLC owns the "Truth" of what the machine did (e.g., Torque achieved: 5.4Nm). MES records this value for history, but the PLC performs the immediate pass/fail judgement.

Pro-Tip: Avoid "Grey Zone" duplication. A common failure mode is managing Bill of Materials (BOM) in both PLM and ERP manually. Automate the interface: PLM (Design) -> ERP (Costing) -> MES (Execution).

Final Checklist

Data Object	Level	System of Record (Owner)	Critical Interface Rule
Sales Order	L4	ERP	MES never creates Orders; it executes them.
BOM / Revision	L4	PLM	Syncs to ERP/MES only on formal Release.
WIP Location	L3	MES	ERP sees only "In Process" (does not see bin/station).
Serial Number (UID)	L3	MES	MES generates and tracks the unique identity.
Process Result (Pass/Fail)	L3	MES	Stored in MES; Summary sent to ERP.
Machine Recipe	L2	SCADA/MES	Do not hardcode recipes in PLM documents.
Sensor Telemetry	L1	PLC/Edge	High-frequency data stays at L1/L2; only summaries go to L3.
Inventory Count	L4/L3	ERP/WMS	MES decrements inventory and updates ERP.