Faceted Search: a Real World Example

Facets are attributes associated with a given thing. The attributes of a glass of iced tea, for example, include its temperature, volume, and color. Facets have hierarchies of their own. A temperature can be hot or cold; volume can be large or small; color can be varying shades of brown.

Faceted search allows a user to narrow their choices down when searching for something online. This type of search is easy to understand if we look at a real world equivalent. Let's use the example of a car purchase I made in 2012. I blogged about it at the time and I’ll include some quotes here.

So it was time to retire my old, reliable 1999 Saturn station wagon. In the swapping arrangement we’ve established for automobiles, that meant that I’d get my wife’s old car and we’d buy her something new. My wife’s criteria for a new car is pretty succinct: it has to have heated seats and not be white. Simple enough. But there is one other factor to consider: gas mileage.

All of the luxury models I looked at had mediocre to poor gas mileage. Most were in the MPG range of 17 city/25 highway. Disappointing. This applied to all of the entry to mid-level models of Audi, Mercedes, Infiniti and Cadillac that I looked at. With gas prices expected to hit $5/gallon this summer this started to look like a real drawback. A small idea that had been sitting in the back of my head for months started to grow: “what about the Chevy Volt?”.

The Volt’s new, uses new battery technology, has a limited track record, and (most importantly) is expensive for what you get. For a car that looks essentially like an economy model, it costs as much as any of the aforementioned luxury brands. Is a Chevy worth $40,000? I had to think long and hard about that. But the more I looked at the Volt, the more I found to like.

In these paragraphs, I established several facets for my car search:

Seats (possible values: heated or not),
Color (any but white),
Mileage (low vs. high),
Locomotive Source (gasoline, electricity, hybrid),
Manufacturer (Chevy, Audi, Mercedes, Inifiniti, Cadillac), and
Purchase Price (low vs. high)

There were two more facets.

The Volt was completely different. I just felt that it was a game-changer: a car that drove in silence, emitted no pollution from the tailpipe and was not tethered to the pump or the seasonal fluctuations in the cost of gasoline. Plus, it was American made and could be driven on energy from domestic energy supplies. I would not be subsidizing unfriendly foreign governments.

The last facets were Subsidization (am I enriching a foreign or a domestic entity) and Ownership Model (buy vs. lease). We decided to lease.

And in case you’re wondering how it worked out...

We haven’t regretted the decision for a second. We both felt good about the purchase from the beginning and we love being able to plug the car in at night and be ready to go in the morning. The car feels tight, the interior fit and finish feels as solid as a Japanese car and it drives great. The acceleration is strong enough to merge with confidence on any expressway on-ramp and the computerized instruments provide plenty of feedback on the efficiency of your driving. Unlike the Nissan Leaf, we’re not limited to a 100 mile range and can drive the car across the country if we need to. We can always power the battery from the gas generator if necessary. It seems like the perfect compromise.