The ISA-88 and ISA-95 standard consist of several models, for example models of the physical structure of the enterprise, models of production procedures, models of information flows and object models. What is the use of these models?
“A model is a useful representation of a specific situation or thing. Models are useful because they describe or mimic reality without dealing with every detail of it. They typically help people analyze a situation by combining ideas with information about the specific situation being studied. Models help us to make sense of the world’s complexity.”
Steven Alter, Information systems, ISBN 0- 13- 043242-3)
Just communicating about a system can be difficult because different people in the same conversation related to an information system often attach different meanings to common terms. ISA-88 and ISA-95 provide definitions of batch control terminology and enterprise- control system integration terminology. This terminology is presented within models, which explains the relationship between the words. For example, in the physical mode, the process cell is place on a higher level than the unit, which explains that a Process cell has one or more Units.