EDDL: The Feldbus War that won't go away

July 25, 2005
Fieldbus guru Dick Caro on EDDL: “At one time, there was a need for FDT/DTM, but that time has passed. EDDL [Enhanced Device Description Language –ed.] is a superior solution. There is nothing simple about FDT/DTM. It is a very complex implementation that is based on ActiveX objects, with all of the hazards that entails. EDDL is implemented as a text-based (actually an XML file) database resident on the field device, or downloadable from the internet or a CD. The HMI or engineering workstation interprets the EDDs of the device and uses this to form the visual display consistent with the host system or DCS. In real-time, the same EDD-defined data tags are used for the transfer of data.“However, the end user considerations are paramount. Emerson's view is that a consistent HMI view of field devices as determined by the DCS/HMI supplier is better for the end user. The FDT viewpoint is that the field device manufacturer is better qualified to configure the HMI view of their devices. I agree with Emerson on that point.“Emerson also asserts that EDDL is needed for real-time device access anyway, so why is another method needed for engineering use only during device configuration? Good question!“Bottom line. Emerson is not going to support FDT/DTM on Rosemount instruments and Fisher valves unless they lose market share. I don't think that FDT/DTM has any end user features to cause a buyer to reject Rosemount/ Fisher in favor of some other instrument supplier that does support FDT/DTM.“My market analysis is that FDT/DTM, while being a fine technology, is doomed.”