The ISA-95 Enterprise/Control System Integration standard defines five levels of activities in a manufacturing organization. Generally, automation and control support Levels 1 and 2, MOM systems support Level 3, and business Enterprise Resource Planning (ERP) systems support Level 4 activities. The ISA-95 levels are shown in Figure 1.

• Level 0 defines the actual physical processes.
• Level 1 elements are the sensors and actuators attached to the control functions in automation systems.
• Level 2 automation and control systems have real-time responses measured in sub-seconds and are typically implemented on Programmable Logic Controllers (PLC), Distributed Control Systems (DCS), and Open Control Systems (OCS).
• Level 3 typically operates on time frames of days, shifts, hours, minutes, and seconds. Level 3 functions also include maintenance functions, quality assurance and laboratory functions, and inventory movement functions, and are collectively called Manufacturing Operations Management. A wide variety of systems support the activities, including SCADA (Supervisory Control and Data Acquisition) systems for monitoring the process and providing operator control, batch control systems for execution of recipes, data historians for the collection and preservation of time based data from Level 2 systems, recipe and document management systems for managing recipes and workflow instructions, detailed scheduling, campaign management or work dispatching, and work or product tracking.
• Level 4 typically operates on time frames of months, weeks, and days. Enterprise Resource Planning (ERP) logistics systems are used to automate Level 4 functions. Level 4 is called Business Planning and Logistics.

Figure 2 - Five Activity Levels in Business

It is important to remember that each level has some form of control and each level has its own definition for real-time. Level 3 systems consider real-time to mean information available a few seconds after shop floor events occur. Level 4 systems consider real-time to mean that logistics and material information is available daily or within a few hours after the end of a shift.

ISA-95 typically deals with information exchange across Level 3 systems or between Level 3 and Level 4 systems. Specifically this would involve information exchange between ERP, EAM, CMMS, MES, WMS, LIMS, PLC and DCS systems. This information exchange in real-time is often required in order to allow workflows and recipes to execute in a timely manner. ISA-95 defines four primary types of information that often must be exchanged among MOM systems and between ERP systems and MOM systems, these types are; information about material and the properties of materials, information about equipment as it pertains to the operations being performed, information about the physical assets that make up the equipment, and information about personnel and their roles and qualifications.