What is JMF?

The Role of the Job Messaging Format

So far we've talked about JDF MIS, or workflow systems, and devices on the floor. The MIS or workflow system acts as the JDF agent. It may communicate with and command a controller. The controller is an important concept in JDF. A controller for a device on the floor may be embedded, a separate physical device, or actually in control of more than one device. We have even seen a couple of "departmental" controllers enter the market that deal with all the devices in a department (e.g., postpress).

The language used to communicate between JDF agents and controllers is the Job Messaging Format (JMF). JMF is part of the JDF specification. JMF also is built in XML and is part of the JDF schema. JMF allows a controller to communicate to a JDF MIS or workflow system information, such as events (start, stop, error), status (available, offline, stalled, etc.), results (count, waste, etc.), and other details, such as who is the current operator.

A controller may also "register" with a JDF MIS or workflow system letting it know it is available. Where a controller controls multiple devices, it can provide registration information for the devices it supports. Note: This is information like make and model and is not a substitute for device capabilities as described above.

An MIS or workflow system may use JMF to command devices on the shop floor and may even be able to change the order of jobs in the queue. You may have noticed the heavy use of the word "may." In the JMF session you'll learn more about the options in JMF and the various levels of support a controller may provide for JMF. JMF messages may also be unidirectional (the MIS system provides the commands, but the controller does not respond) or bidirectional. Determining what JMF options will be required of your process automation strategy is an important part of creating an effective JDF equipment buying policy.

JMF can also be used by one controller to provide commands to another controller. This is an important feature for supporting combined process and pipelining as described above.