MES and ERP solve different layers of the manufacturing stack. ERP plans and accounts for the business (orders, MRP, inventory, finance), while MES orchestrates and records what actually happens on the shop floor. In regulated, brownfield plants they typically coexist, with tight integration, clear system-of-record boundaries, and validated interfaces.

ISA‑88 (often referenced as S88.01) is a batch control standard that defines models and terminology for designing and integrating batch manufacturing systems. It does not guarantee compliance or interoperability by itself, but provides a common structure for equipment models, recipes, and procedural control that must be carefully interpreted, implemented, and validated in each plant.

ISA-95 (ANSI/ISA-95 / IEC 62264) is an international standard that defines models and terminology for how enterprise systems and manufacturing systems exchange information. It helps clarify system roles and data flows in brownfield plants but does not prescribe specific architectures or guarantee consistent vendor interpretations.