One of the key tools that lets standards bodies create more precise standards is the Unified Modeling Language.

UML, itself an ISO standard from the International Organization for Standardization, has been used to create standards such as the Instrumentation, Systems and Automation Society’s ISA88 and ISA95 standards, as well as the PackML standard created by the Open Modular Architecture Control (OMAC) Users Group. Using UML to describe facets of specifications has done a lot to eliminate a vexing issue for volunteers trying to come to a consensus on complex issues—helping organizations finish standards in a timely fashion. That’s in part because UML’s models provide precision and eliminate the back-and-forth questions over the meaning of terms.

“UML provides a standard way for describing and defining complex systems. It represents in pictures what it would take several sentences to describe. With diagrams, you can concisely say in exquisite detail what you’re trying to do,” says Dennis Brandl, senior consultant at BR&L Consulting Inc., of Cary, N.C., who has played key roles on both the ISA95 and ISA88 standards committees.

Broad usage

UML has played a major role in the development of many standards. It’s only been about a decade since the many object-oriented modeling techniques were brought together under the auspices of the Object Management Group, so its impact doesn’t go back too far. But standards bodies were early adopters, once UML became available. “Parts 2, 3 and 4 of ISA88 use UML modeling. It wasn’t around for the first part. Part 4 uses formal models that contain a level of detail not provided in the other parts,” Brandl says.

Though the ISA88 developers jumped on the bandwagon early on, their initial efforts came close to being categorized under “more pain than it’s worth.” As with many jobs done with computers, getting started wasn’t always the easiest of jobs. “It’s fair to say it took longer to develop the standard because we used UML. There is pain up front, but it pays off in the end,” Brandl says.

If any group is aware that adopting a single approach that has been agreed to by a number of people is difficult, it’s standards bodies. Successes in many of the initial UML-based development projects led to widespread usage in this influential community. Some of these projects extend into areas that weren’t considered when UML was created.

However, that doesn’t mean that the language can’t be stretched. “Some of the macro states in PackML were a little difficult to describe in formal UML, so we took some liberties,” says Rick Morse, software business manager at vendor Rockwell Automation Inc., in Mayfield Heights, Ohio. “Some of the work in ISA88.5 takes things further with macro states, breaking the confines of what UML offers.”

He notes that when rules are stretched or broken, UML tools offer cross-checking. “Cross-checking between formats works like a good compiler check. The tools give us a sense of whether we’ve forgotten anything or left out large sections,” Morse says.

E pluribus unum

In standards bodies, as in many aspects of the business world, making it simple to keep everyone on the same page is a critical factor for successfully creating an end document. UML’s ability to relay explicit information eliminates confusion. But observers note that its benefits don’t extend further than that.

“UML eliminates ambiguities. It’s done so much to show a better way, as it provided a commonly understood unifying tool,” Morse says. “It’s not a silver bullet that solves any work that needs to be done, but it eliminates the time spent tripping over the way we communicate.”

Avoiding the time-consuming aspect of clarifying communication is a huge benefit, particularly when disparate groups are involved in the development of a standard. The volunteers who create standards come from many different fields, which helps bring richness to the end document. Their broad range of expertise correlates to a wide range of terminology and various levels of understanding in different fields. The benefit of the clear visual representations inherent in UML presentations is huge in this environment.

“A lot of people working on standards are not software engineers. They are subject matter specialists. Often, there are people looking at aspects that they don’t understand,” Brandl says.

Increasingly, these subject matter experts are located on different continents. That brings up yet another type of incompatibility. Language barriers are dramatically reduced when graphical representations are used. “The biggest benefit is that it provides a consistent way of communicating across a very divergent group, which ...