There is a lot of talk today about the integration of the “enterprise” and the “factory floor.” I have enjoyed a lot of this discussion. …
There are also new terms being thrown around like digital factory and integrated intelligence. However you look at it, there is more and more talk (and action) toward linking the factory floor with systems not directly involved in factory floor control. The enterprise systems can be big and sophisticated like enterprise resource planning (ERP) and manufacturing execution systems (MES), or they could be as simple as a recipe manager on your server that downloads 20 tags once a day.
No matter what you are doing, there is a key distinction between the systems on the factory floor and in the enterprise that many people do not understand. This difference is what I term “loosely-coupled” and “tightly-coupled” systems. I do not believe these are new concepts, but I also do not think they have been examined in the light of the current trend toward the integration of factory floor and enterprise systems.
I would argue that factory floor systems should be labeled tightly-coupled. Systems that use Profibus, Profinet IO, DeviceNet, EtherNet/IP, or any Modbus version have a strict architecture. These are really I/O systems as much as the folks at the trade associations would have you believe otherwise.
… loosely-coupled systems provide exactly the right kind of interface for enterprise communications. Loosely-coupled systems decouple the platform from the data, the data from the data model, and provide a much more dynamic mechanism for moving data.
Loosely-coupled systems have these kinds of characteristics:
- Widely-used, Standards-based Transport Layer – Messages are transported in loosely-coupled systems with open, widely implemented, highly flexible transport layers, including TCP and HTTP.
- Open, Platform Independent Data Encoding – Data is encoded using an open standard data encoding like eXtensible Markup Language (XML) that can be processed by any computer platform.
- Highly Extensible Operating Interface – The interface between loosely-coupled systems is flexible and extensible. Simple Object Access Protocol, or SOAP, is the main interface, and it provides a highly flexible mechanism for messaging between loosely-coupled systems.