As for the term MES, it is a term that was defined by AMR, 15 years but does a very bad job describing the actual functionality set in general or in a vertical industry way. It is the most highly misunderstood term in manufacturing software. Ask 100 people, you will get 100 answers. Ask the same 100 people what Production Operations Management (POM) is, 50 will have no clue but take a close guess; the other 50 will refer to the ISA 95 Part 3 Activity definition, which describes the actual functions, tasks with functions and data exchanges between functions. No "MES" definition does this. Even AMR now is using the term Manufacturing Operations System (MOS), which is a system abstraction from ISA 95 Part 3 instead of their own MES term, since it includes POM and Quality Operation Management (QOM) and Inventory Operations Management (IOM). When Maintenance Operations Management (MaintOM) activity model is included, these four activity models (POM, QOM, MaintOM, and IOM) define all the Manufacturing Operations Management (MOM) activities (functions, task, and data exchanges) in the Purdue manufacturuing functional model's Level 3. ISA 95 Part 3 is THE document that 4 out 5 manufacturer are using worldwide to define their systems in their Requests for Proposals (RFPs).