1.3 System Landscape & RACI (ERP/MES/QMS/WMS/PLM/SCADA)

A manufacturing floor running on undefined system boundaries guarantees data corruption. When an ERP attempts to read millisecond sensor data, or a PLC tries to query financial ledgers, the "Single Source of Truth" disintegrates. You must strictly define the architectural layers based on Data Granularity and functional domain, ensuring every data point has exactly one Master Owner.

The Core Trinity: ERP, MES, PLM

Modern manufacturing relies on three pillar systems. Do not force one tool to do the job of another.

ERP (Enterprise Resource Planning)

The Domain: Finance, Inventory, Procurement, and Order Management.
The Question it Answers: "Why are we building this, and how much does it cost?"
The Boundary: ERP stops at the warehouse door. It knows you have 1,000 screws, but it does not know which specific screw went into which specific product.

PLM (Product Lifecycle Management)

The Domain: Engineering Design, BOM (Bill of Materials), CAD, and Revision Control.
The Question it Answers: "What are we building?"
The Boundary: PLM owns the definition. It creates the "Digital Twin" of the product structure. It pushes data to ERP and MES but never executes production.

MES (Manufacturing Execution System)

The Domain: Production Control, Quality, Genealogy, and Machine Connectivity.
The Question it Answers: "How is it being built right now?"
The Boundary: MES executes the work. It is the bridge between the digital definition (PLM) and the physical reality.

The Single Source of Truth (SSOT)

Data duplication is the enemy of integrity. Establish a "System of Record" for every critical data object. Any other system that needs this data must be a "Subscriber," never an editor.

The Ownership Matrix

Customer Demand: Owned by ERP.
- Logic: Sales enters the order in ERP. MES sees it as "Scheduled," but cannot change the quantity or due date.
Product Definition (BOM): Owned by PLM.
- Logic: Engineers release Rev A in PLM. ERP calculates cost; MES validates assembly. If a shop-floor user changes a part manually in MES, the loop is broken. Forbid this.
Unit History (Genealogy): Owned by MES.
- Logic: The MES generates the unique serial number (UID). ERP only knows that "one unit was finished." The MES holds the granular history (who, when, which machine).

Pro-Tip: Beware of "Excel Glue." If your Critical Path relies on a spreadsheet managed by a planner to translate ERP orders into MES schedules, your architecture has failed. The data flow must be automated and API-driven.

Data Flow Strategy: Push vs. Pull

Define how data moves between the pillars to prevent synchronization lag.

Master Data (Push)

Static data (BOMs, Part Numbers, Users) should be Pushed from the Owner to the Subscriber upon release.

Example: PLM releases a new BOM -> Triggers immediate update in ERP and MES.

Transactional Data (Event-Driven)

Dynamic data (Inventory Consumption, Status Updates) should be Event-Driven.

Example:
- If Operator finishes a unit (MES Event) -> Then MES instantly decrements local WIP.
- Then MES accumulates these events and sends a bulk "Production Declaration" to ERP (e.g., every shift or hourly).

Shadow IT and the "App Trap"

Well-meaning engineers often build isolated apps (PowerApps, SQL scripts) to solve local problems. While innovative, these create "Dark Data" silos that the enterprise systems cannot see.

The Containment Rule

If an app generates data required for audits (Quality Pass/Fail, Traceability) -> It must integrate with the MES.
If an app is purely for visualization (Dashboarding) -> It can read-only from the Data Lake.

Final Checklist

Data Object	System of Record (Owner)	Consumer (Subscriber)	Critical Rule
Sales Order	ERP	MES	MES cannot create or delete orders.
BOM / Route	PLM	ERP, MES	Engineering Change Orders (ECO) start in PLM.
Inventory ($)	ERP	MES	ERP owns the asset value; MES owns the location.
Unit Traceability	MES	ERP (Summary)	MES owns the unique Serial Number history.
Quality Limits	PLM/MES	Machines	Machines execute limits; they do not define them.
Costing	ERP	Sales	MES sends "Time Spent" to ERP for cost calc.
Equipment State	MES/SCADA	Maintenance	Do not rely on ERP for machine downtime tracking.