When I’m working with organizations, I see many of them struggle to make sense of what ANSI/ISA-95 has to say about Enterprise Control System integration, what it really means, and how that reflects on the requirements/design of an integrated solution. Part of what I think helps is an 8-step prototype plan. Not only does it help make sense of levels 1-4 integration, but this also helps the team to understand opportunities and limitations with existing business processes.
You can see the prototype plan and learn more about the implications of ANSI/ISA-95 in this Emerson Process Experts blog.