Nomenclature vs. Classification – Part 1

May 7th, 2013 / By Ron Mills, PhD

When our esteemed Medical Director is about to make a pronouncement about something outside his vast area of expertise, he usually starts by saying, “I’m just a country doctor, but …”

Well, I’m just a country computer programmer, but I think we should discuss the difference between a nomenclature and a classification. “Nomenclature” is the “N” in SNOMED. “Classification” is the “C” in ICD-9 or -10.

Why am I wandering into such dangerous waters, swarming with medical informaticists and other academic denizens capable of biting my head off, or at least splitting all my hairs? Because many people, in their desire to have an easy ICD-9 to ICD-10 transition, are setting their expectations of the GEMs too high. This manifests itself as requests for otherworldly extensions to software that I helped write. And though I’d do almost anything to keep my customers satisfied, I’m not a magician.

So here goes. Suppose you are Imelda, with 7,000 pairs of shoes. You need to be able to talk to your servants about them. Shoes can be described structurally (pumps, stilettos, slippers, boots) or by where they are worn (parties, state dinners, bedroom, tennis court) or by color (black, blue, red, gold) or material (leather, silk, canvas, diamond-studded) or by manufacturer, designer, year of acquisition, height of heel, degree of funkiness—the human brain is good at inventing types of distinctions. After all, every patient—oops, pair of shoes—is different, right?

Your life is further complicated by the fact that your servants don’t all speak the same language. So you start with your favorite distinctions and invent a Standardized Nomenclature of Footwear (SNOFOO). Each important shoe concept, like “stiletto,” is given a Footwear Identifier (FID), and the word or phrase for it in each of the servants’ languages is associated with it. So you can be confident that when someone speaks of FID 24620, they mean “stiletto” the same way you mean it, even if they say it differently in their own language.

Or do they? When a new servant asks you how to tell if a shoe is “stiletto” as opposed to just “high-heeled,” you explain that the heel must be at least eight centimeters high with ground contact no more than a square centimeter. When she asks, “What is ‘heel’ and what is ‘centimeter? ’” you go back to SNOFOO and add “is-part-of” and “measurements” and “is-a”—as in, “stiletto” “is-a” “heel” “is-part-of” “shoe.” Pretty soon you have enough FIDs in SNOFOO so you can say “every concept FID is defined through its relationship FIDs with other concept FIDs,” which cows those pesky servants into silence (but doesn’t answer their question). On the other hand, having to buy every servant a laptop to access each shoe’s Electronic Footwear Record (EFR) is a strain on your budget, but as long as the machines are put to Meaningful Use—communicating accurately about your shoes—you are okay with it.

With SNOFOO, you can be confident that the EFR entered by a servant who only speaks Azerbaijani will be understood by another who only speaks Bengali, since the EFR contains neither Azerbaijani nor Bengali, but consists solely of FIDs. Well, it did, until the official palace historian started writing such wonderful descriptions (in English) of the shoes you wore each day, making subtle distinctions beyond SNOFOO’s ability to capture them. So you had to allow some free text in the EFR to preserve the subtleties. And before long, even the servants were finding justifications for using it. This would have bothered you, except that after watching Jeopardy! you started to believe that computers would soon be able to understand the free text and translate it into Enhanced SNOFOO.

At this point, SNOFOO started to have many of the features of a natural language—circular definitions, multiple ways of saying the same thing, recognizable styles of expression—and needed a committee of experts to keep it pure. You begin to wonder if you wouldn’t have been ahead of the game just to buy everyone English lessons.

Nevertheless, you have a nomenclature: a standardized way of naming things. Using pick lists, you can enter into your computer:

Bring me

Structure: ballet slippers

Material: silk

Color: gold with silver piping

Acquired: March 1998

Source: Duke of Hazzard

and whichever servant is on duty today will know exactly what you are talking about. Whether he can find it or not is another story altogether. A story for part two of this blog series.

Ron Mills is a Software Architect for the Clinical & Economic Research department of 3M Health Information Systems.