Reader Feedback: Keeping it simple

I saw the editor’s note, “The Virtues of Simplicity,” in the April issue. Repeating the patterns of behavior of the past three decades in process automation will, not surprisingly, yield similar results. Requirements for well-refined information and actionable knowledge will continue to rise. Buying best-in-breed is a consumer behavior that will continue in a laissez-faire economy–and thank goodness for that. How we as an industry reconcile these seemingly contradictory forces of “simplicity” and “best-in-breed” will greatly impact the eventual outcome. 

The old infrastructure–all $65-billion-plus of it–is rapidly deteriorating and needs to be replaced. The supply-demand scale of automation professionals is in a state of imbalance, and the end-user community is screaming loud and clear, “Simplicity.” As one of my all time favorites, Bob Seger, says in his latest album, “Simplicity…is good for me…” and it is surely good for everyone in the automation industry.

Eddie Habibi, Founder & CEO, PAS, EDDL, FDT/DTM and FF DTMs

I read with interest Dick Caro’s post in the April 23, 2007, Sound Off! blog on ControlGlobal.com on the subject of  EDDL vs. FDT/DTM. I think there is a large issue to be considered here that most observers have been missing. EDDL generates an interpretive binary which has limited capabilities and operates through a host’s “built-in” interface routines to access the devices. DTMs, on the other hand, are Microsoft-hosted programs designed to access the devices directly via each protocol’s native messaging. While that means that EDDL is more limited in what it can do than DTMs, there is a flip side. EDDL is restricted from doing harm to devices, while DTMs are not.

This “harm” is primarily a concern for Foundation fieldbus (FF) because FF devices are configured for control and often integrated into a control system that accepts responsibility for their configuration. Hence the DTM author has the ability to send messages that could alter the device configuration. DTMs also tend to bypass the control system’s parameter access control mechanism and its centralized recording of configuration and operational changes, and can de-synchronize backed-up databases needed for restoration, etc.

A potential partial solution that I have been promoting through the Fieldbus Foundation is to create a different VCR for diagnostic host connections. Then the device would know which host is which and would be expected to disallow actions that could alter its critical configuration.

Another potential solution would  require DTMs to interface to the primary host’s OPC port so the primary host can provide browse and parameter read and write services, access controls, change recording and database synchronization. OPC services are inherently less risky with respect to the configuration alteration potential. Since there are no certified DTMs for FF today, there should be no issues with such proposed changes.

Bill Hodson, P.E., Honeywell - Industry Solutions, Fort Washington, Pa.