ERP
ERP typically owns enterprise transactions such as sales demand, purchasing, inventory accounting, finance and higher-level production orders or plans.
MES/MOM
MES adds manufacturing execution context: order dispatch, operation progress, material genealogy, quality checks, WIP, labor/resource status and production performance.
SCADA/HMI
SCADA and HMI systems supervise processes and equipment, show real-time states and alarms, and provide operator interaction close to automation.
PLC/control
PLC, DCS and other control systems execute machine or process control logic. MES should not become a substitute for safety- or control-critical logic.
Integration boundary
Interfaces should exchange the minimum authoritative data needed at each boundary. Duplicate ownership creates reconciliation problems, especially for master data and production status.