News and comment: EDDL team reorganizes for FDI

EDDL Cooperation Team reorganizes itself to become FDI. New unified technical and functional specs scheduled for 2010.

Peter Welander

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In one of the great "why can't we all just get along" efforts within our industry, the EDDL (Electronic Device Description Language) and FDT (Field Device Tool) groups are working toward building a unified standard that intends to advance the ability to work with ever-more-sophisticated field devices and operate with both integration platforms. The latest news is that the EDDL Cooperation Team has expanded and rebranded itself the FDI (Field Device Interface) Cooperation Team, looking ahead to the name of the new standard in the works.

The EDDL group originally included three main organizations at its core: Fieldbus Foundation, HART Communication Foundation, and Profibus User Organization. In 2004 and 2007 respectively, it added the OPC Foundation and FDT Group. Now a group of device and control system suppliers has joined, including ABB, Emerson, Endress+Hauser, Honeywell, Invensys, Siemens, and Yokogawa. These supplier companies have agreed to support FDI solutions in their systems and products and will provide resources for the completion of this project.

We have discussed the competing FDT and EDDL technologies in a number of articles in Control Engineering , and even a podcast . We have also discussed the benefits of blending two technologies that are close but incompatible. NAMUR has also pushed for the confluence . As the organization puts it in rather direct terms:

"Field device integration in the process industry has involved the competing concepts of EDDL and FDT/DTM for more than a decade. NAMUR recommendation NE105‘Specifications for integrating fieldbus devices in engineering tools for field devices,' was published as early as 2004 to clearly define user requirements for equipment integration. To date, neither of these two concepts meets the most important user requirements. As matters stand these two concepts can be expected to harbor long-term disadvantages for both users and manufacturers."

Negotiations have been going on by fits and starts since the platform integration efforts were launched at Hannover Fair in 2007. The most recent progress report which was delivered in the Fall, 2009 issue of (Foundation) Fieldbus Report said:

"Recent FDI working group activities have focused on fulfilling functional specification requirements. Validation of technical specifications is scheduled for early next year, with release of the final FDI functional specification planned for the middle of 2010. Major control equipment suppliers and user organizations are cooperating on an FDI framework supporting the growth of intelligent instrumentation technology around the world."

While this FDI work is justifiably lauded by all involved, it will not result in one big system that will work for everything, nor is that really its intent. If you understand how the systems work, you'll see why. In some respects, FDI is the next generation of the device descriptor. This system has evolved to keep up with the growing sophistication of smart devices. As the number of configurable parameters has grown, and with the addition of soft parameters, the system that enables the device to describe itself to the person doing the configuration and to the control system has had to grow too.

According to Hartmut Wallraf, Technology advisor for Invensys Operations Management and chairman of the FDT Group , FDI is adding support for a new range of capabilities. (See diagram.) He says, "In FDI there will be two parts: An interpreter for the device description part, and a compiled functionality for the business logic and user interface. FDI required functionality is the description of a device, defining all the configurable parameters in a descriptive environment. Then there are business logic and user interfaces which are optional, and these two are more like FDT provides with DTM technology. The FDT Group and FDI are synchronizing and unifying the way of building these business logic and user interface functionalities using the same techniques."

This doesn't mean everything will blend together. Devices will still have a DTM along side the FDI software. Even if your control platform uses FDT, you still need EDDL (or soon, FDI) to do the initial configuration. One of the additional benefits of FDI is that it reconciles differences in the DD code between HART, Foundation Fieldbus, and Profibus platforms.

"FDI is still a descriptive-based technology, where FDT is an application," Wallraf adds. "This means a DTM is a program or application which runs in an infrastructure based on Microsoft technologies. This is the fundamental difference because DDs have been defined from the beginning as infrastructure independent. This independence was a key requirement. The FDT group decided that for more complex functionalities coming with intelligent field devices, an application is required. FDI will not supersede the application part of a DTM. FDT does not depend on the communication technology, nor is it only for process automation."

The bottom line is that the FDT group will continue to develop its technology and offer its complete package to system builders and end users. It will use FDI for device configuration, but ongoing management will use DTM. The DTM may access some information from the FDI, but the extent of that will vary.

Companies that prefer to develop their own device integration platform can continue to work with EDDL and FDI information within their own program frameworks, hence the importance of infrastructure independence. Some DCS builders, Emerson for one, have designed their own integration platforms using EDDL rather than adopting FDT's package. Users can choose the approach that seems most appropriate for the application. Hopefully the practical result going forward is that users won't have to pay attention to whether a field device is compatible with one or the other system.

Time will tell if these efforts, continuing in parallel, will ultimately fulfill the equipment integration objectives users want and those outlined by NAMUR. At least field devices can be agnostic if they offer both FDI and DTM information, which is apparently the intent of the manufacturers in the group. The ability to deliver the functionality that users want will still depend on the larger system designers or the FDT Group.

-Peter Welander, process industries editor, PWelander@cfemedia.com
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