Lately I've been searching for just the right portable CD player to take on the train. I want one that plays MP3s and includes a FM radio. I'm a big fan of Amazon, but I was frustrated trying to search for a CD player with all these characteristics.
I tried searching using the terms "CD FM MP3", but still ended up with some products that didn't offer what I wanted. Amazon provides quite a few browse options, but of course, I could only browse one feature at a time, and so was left sifting through the results to find the right combination.
I happened to have a gift card for Circuit City, so I popped over to their web site, and low and behold, they included an option to refine the search by brand, radio built-in, MP3 capable and car kit included. Just what I needed! A faceted classification!
When designing databases and search interfaces, it's important to consider whether you will need a faceted classification. A recent paper by William Denton, "How to Make a Faceted Classification and Put It On the Web" describes the concept in some detail.
I'm not going to lie to you. The paper makes for dry reading. It is, after all, a library school paper. And you might walk away from the article thinking that faceted classification applies to the description of physical items only. But in reality, faceted classification can be an important consideration for KM projects when you want to provide more than one way to view data and allow more specificity than you might get with full-text searching.
When would you use a faceted classification? According to Denton, "Facets will handle three or more dimensions of classification. When, for the purposes of the classification, it is possible to organize the entities by three or more mutually exclusive and jointly exhaustive categories, then facets are probably the appropriate classification."
He describes four general principles when desigining facet-based navigation:
The user should not be able to form a query that is known to have no results.
Users must always know where they are in the classification
Users must always be able to refine their query or adjust their navigation to see what is nearby in the classification.
The URL is the notation for the classification.
For more information on faceted classification, see The Knowledge Management Connection's page on faceted classification which addresses it in terms of organization knowledge rather than physical attributes. Still, sentences such as "The absence of polyhierarchy is implied, at least, by having mutually orthogonal facet hierarchies" can bring on the dreaded library school flashback, as does the repeated references to Raganathan.
In the meantime, I'm can't make up my mind WHAT I want. Maybe my perfect CD player is actually an IPOD. I guess there really is such a thing as too many choices.