On the Internet Evolution weblog Rob Geier presents some interesting findings from an Informationweek survey about Rich Internet Applications. According to the survey, the most important reason to use RIAs is improving the Customer Experience. Although management dashboards and customer support are also popular, many companies are already building RIAs for self-service and e-commerce.

Rob’s main RIA example is Home & Abroad, a personalized travel site. If you have a couple of minutes, use the ‘Quick Planner’ to see how they suggest a trip itinerary based on your preferences: pretty cool.

However, when I started editing my itinerary I wasn’t very impressed with the user experience. Until I realized why I wasn’t impressed:

► All travel planning sites need great faceted search!

And that’s what Home & Abroad is missing. I scoured the internet for some other examples. I found some good sites via the excellent Web 2.0 Travel blog and Travel+Leisure’s Top 25 Travel Sites. But let’s first define what we mean with Faceted Search.

What is Faceted Search?

Faceted search allows you to narrow down search results with multiple filters, so you quickly see which search results are most relevant to you. This is especially useful for structured search, where you know the important search criteria beforehand. For example, you may want to filter a flight on price, number of stops, and the total flight duration. Unstructured search – like Google – is not a good candidate for faceted search.

These are some good examples of faceted search for attractions, flights and hotels:

Faceted search at Home & Abroad, Farecast, InsideTrip and Kayak

Focus on Meta-Search Engines

Most usability innovations seem to take place on meta-search engines, such as Kayak, Farecast and InsideTrip. These websites search multiple sites for flights, hotels and cars and present the results in a single screen. They make money with referral fees and advertisements. They exist because of their superior user experience compared to established sites such as Expedia and Travelocity and Orbitz.

Based on the analysis of several faceted search tools, I’ve tried to distill some best practices for faceted search, and I’m proposing the following top 10 rules for faceted search. Let me know your feedback!

Faceted Search Best Practices

1. Combine Search Criteria

Faceted search got its name because you can combine various search criteria (‘facets’) to narrow down the search results. So technically Home & Beyond doesn’t have faceted search, because the search criteria cannot be combined. You can’t see ‘Buildings & Monuments’ that are cheaper than $5. You either see all buildings, or any attraction cheaper than $5. So the ability to use multiple search criteria at the same time is of key importance for faceted search applications.

2. Use Flexible Ranges

If you can specify prices or flight times, it’s great if you can set a lower and upper threshold, rather than select a pre-defined range, such as $10-$20 or ‘afternoon’. Kayak has introduced a great tool for this: the double slider (see picture), which is now also adopted by other sites. Move the sliders to narrow down your choices.

3. Use multi-select for non-numeric filters

If there are multiple categories to choose from, it’s useful if you can select more than one category. This is illustrated with the airline selection tool from Farecast (pictured below). They even add ‘clear’ and ‘show all’ shortcuts.

An elaborate example is from InsideTrip, where you can refine their trademarked TripQuality rating, based on Speed, Comfort and Ease categories, see screenshot below.

4. Use Keyword Search if there are too many possible options

In some cases you may have more than a couple of dozen options. For example, if you go to Orlando and want to stay in a Disney hotel, you can search for the keyword ‘Disney’. It’s not possible for the creator of the faceted search tool to think up all possible search terms upfront. For example, in other cities other search terms will be popular. And of course, it should be possible to combine keyword search with all other search criteria. Look at how Kayak hotel search shows hotels costing more than $130 and contain the word ‘Disney’ in their name:

5. Expand to show more details

In the listing of the search results you should include the key pieces of data, but you cannot show everything. If visitors want quick info without leaving the search screen, you can provide a ‘details’ slide-out window. I found that InsideTrip was able to squeeze the most information in such a window, without creating information overload. In the screenshot below you can see that they put a lot of flight quality information in their search results, because that’s their unique approach.

6. Sort the results by Criteria

Even when you’ve used all your facets to narrow down the search, you may still have dozens of options. Therefore, it should be possible to sort the results. Here I’ve sorted hotel results on their proximity to DisneyWorld:

7. Use different views on the data

The default way to present search results is the list grid. It shows a selection of the available information, and you can sort based on this information (see rule 6). But what if you want to see hotels on a map? Or if you prefer to see flight prices for different times of the day? Then the list view just doesn’t do it. Above you see that Kayak offers the Map and Photo view for hotels, and below you see that the Farecast time grid shows you the cheapest time of the day.

8. Show total and filtered number of results

It is easy to lose track of the total number of results of the search, and how many options remain after you’ve applied your filters. If the site prominently displays how many results are shown, the users know whether they need to apply additional filters. If there are still hundreds of options, it’s probably good to use some more filters. Kayak displays the number of results prominently above the search results:

9. Superfast update of results

It’s actually fun to play around with faceted search, but only if the filters are applied almost instantly. When you have to wait 10 or even 5 seconds for the results to appear, it is suddenly a lot less enjoyable. Most sites use a technology called ‘Ajax’, which makes it possible to update search results without refreshing the page. And usually the engineers who develop the sites are obsessed about performance: all changes to the site will first be tested on performance before they go live.

10. Save search results if you switch between tabs

Many of the meta-search travel planners can be used for flights, hotels, cars and more. If you go on a trip to a specific city, you may need all three of those. However, when you’ve just searched for flights, you switch to hotels, and then switch back to flights, all your search results are gone. It would be nice if those would be remembered!

Conclusion

As I’m writing the conclusion, I realize that some of my coworkers made a very early demonstration project for faceted search for travel planning. It doesn’t have all the cool features that are common today, but it was created five (5!) years ago. Take a look yourself: Backbase Travel Demo.

So if you’re creating a faceted search tool today, check these 10 rules to make sure you’re using all available best practices. However, depending on your application, you may not need all of them. Let me know your feedback, so I can improve these rules!

Of the sites we looked at, Kayak was one of the first to use RIA functionality in a mainstream travel booking site, and they still add a lot of new features. But others are following closely, such as Farecast and Insidetrip. Farecast has an edge with their fare prediction (see picture below), and Insidetrip with their quality rating. Home & Abroad should look closely at those sites to improve their search page.

Farecast Fare prediction