More on Denton’s How to Make a Faceted Classification and Put It On the Web

During a recent slog up tread­mill hill I read through Wm. Denton’s How to Make a Faceted Classification and Put It on the Web.

I feel bet­ter now. After my grad school deja vu expe­ri­ence with Simplified Facet Classification I was despair­ing of ever being able to bring facets to the mass­es. Or in my case to intel­li­gent but not LIS qual­i­fied engi­neers and oth­er tech types.

You’ll still need some back­ground in clas­si­fi­ca­tion to under­stand the details but it’s a great overview that is under­stand­able by peo­ple with some back­ground knowl­edge mod­el­ing. Most web and soft­ware dev types have, often unknow­ing­ly, done a fair amount of infor­mal knowl­edge modeling.

Denton’s straight for­ward style makes his dis­cus­sion clear enough that, bar­ring melt down
over the tech­ni­cal­i­ties of the entity/instance analy­sis and facet cre­ation in steps 2 and 3
you can hand this essay out as back­ground reading.

Section 1: When to Make a Faceted Classification gives a nice overview of where faceted clas­si­fi­ca­tion sys­tems fits into the field of clas­si­fi­ca­tion and orga­niz­ing schemes in gen­er­al. Denton pro­vides use­ful ques­tions to ask when con­sid­er­ing faceted clas­si­fi­ca­tion. It’s refresh­ing to see a con­sid­er­a­tion of facets that also dis­cuss­es when facets are not the best answer to your questions.

In the sec­ond sec­tion Denton divides the actu­al work of cre­at­ing the clas­si­fi­ca­tion sys­tem (facets and foci) into 7 steps. Beginning with Domain Collection and end­ing with Revision, Testing, and Maintenance. (Love to see that word main­te­nance laid out in black on white!) It’s a sim­ple method­ol­o­gy that will get you through the process and give you a work­able sys­tem at the end of the day.

What fol­lows are a few notes on his descrip­tion of the process.

Starting with what I believe is the miss­ing first step.

Defining Your Domain

Step 0: Define the Domain

You must have a sol­id and agreed on def­i­n­i­tion of the sub­ject and scope of the domain
before you start. We are all aware that assum­ing that what’s already in the sys­tem is the
lim­it of the domain that needs to be con­sid­ered but also be care­ful that you do not make
the assump­tion that every­thing dealt with by your web­site or soft­ware should be includ­ed in
the domain for which you are build­ing the classification.

Building the Faceted Classification

The next five steps make up the build­ing the facets and foci part of the process.

Step 1: Domain Collection.
Step 2: Entity Listing.
Step 3: Facet Creation.

Note that you’ll have to do quite a bit of iter­at­ing over steps 1, 2, and 3. The process of col­lect­ing, ana­lyz­ing, and defin­ing always brings to light bits and pieces that were missed in the first (lat­est) go ’round. It’s just a fact of life, so plan for it.

Denton does not dis­cuss the tech­niques of analy­sis that can be used to get from the enti­ty (things) list to the facets (char­ac­ter­is­tics) list. This sort of analy­sis is com­plex and domain depen­dent and IMHO the most com­mon point of break down for many attempts. I’m always on the look out for mate­r­i­al that describes these tech­niques, as well as “real” world examples.

Once you have a sys­tem of facets and foci you have to decide on how to arrange its pieces:

Step 4: Facet Arrangement

I find Denton’s expla­na­tion of this step not entire­ly clear. You may have to explain that
you are now work­ing with both the foci (terms) and facets. The end result of this step will
be a list of facets and and arrange­ment of the foci with­in each facet. You will definitely
have to reit­er­ate that the foci with­in each facet are arranged in a way that best reflects
the sub­ject of the indi­vid­ual facet. Once again — the things inside one facet don’t have to
be arranged in the same way as the things inside anoth­er facet. (Can you tell that I’ve had
trou­ble with get­ting this across? Database jock­eys are the worst. Facets and foci do not
map well onto tables, fields, and joins.)

Step 5: Citation Order

Citation order is of less impor­tance in an elec­tron­ic sys­tem than it was in the paper
sys­tems in use when faceted clas­si­fi­ca­tion was first invent­ed. Though you may find yourself
in a sit­u­a­tion in which you aren’t going to be able to take full advan­tage of the
flex­i­bil­i­ty of a com­put­er based sys­tem to mix and match your facets for tech­ni­cal or bud­getary rea­sons. No mat­ter how flex­i­ble your sys­tem is you are going to have to decide on a default dis­play order and behav­ior so don’t skip this step entire­ly but don’t allow any­one to get hung up on it either.

Apply the Faceted Classification 

Step 6: Classification

And now we get to the whole point. Applying the clas­si­fi­ca­tion sys­tem to the stuff. And
it’s about as sim­ple as Denton makes it sound. Sometimes…

Before hand­ing this task off to the near­est con­ve­nient, unoccupied,warm body take a clear
eyed look at how many of your facets include terms (foci) that will require judg­ment calls
to get things labeled prop­er­ly. Who’s best qual­i­fied to make these judg­ment calls in a way
that will serve your ‑users-?

Checking it twice, Getting it on the road, and Keeping it running

Step 7: Revision, Testing, and Maintenance.

Note that you have been doing iter­a­tive test­ing and revi­sion through out the cre­ation of
the sys­tem. If you’ve got­ten here with­out hav­ing to rethink or redo any part of your system
you are one of: work­ing in a very lim­it­ed well-know domain, very lucky, not paying

Actually only revi­sion and test­ing should be includ­ed in step 7. Maintenance should be step
8. Any clas­si­fi­ca­tion sys­tem that does­n’t include main­te­nance as sep­a­rate, on-going phase
is bound to suf­fer ROT.

The final sec­tion: How to Put the Classification on the Web tack­les the ques­tion of how to use your new faceted clas­si­fi­ca­tion scheme to help your users nav­i­gate the stuff. I’ll be dis­cussing Denton’s help­ful sug­ges­tions in anoth­er essay.


If I were hand­ing this out ’round the table in a con­fer­ence room packed with devs and coders I’d leave out the third sec­tion titled: “How to store the faceted sys­tem in a com­put­er”. The tech­ni­cal Ways, Whys, and Wherefore’s of stor­ing and access­ing meta­da­ta such as a faceted clas­si­fi­ca­tion sys­tem go far beyond what is cov­ered by Denton’s cou­ple of pages of X(F)ML and SQL exam­ples. It nev­er pays to drop a shal­low solu­tion to a prob­lem into a room of peo­ple who are trained to take any prob­lem laid before them and debate the best way to do it.

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