"Dave" wrote to TidBITS Talk:
> Aside from the humourous result from assuming that linking authors is
> enough to conclude that someone who bought Adam's wireless networking
> book would be interested in a book on SPSS, it got me thinking about
> the various attempts to find common ground. I've tried a couple
> sites [1] that recommend news articles, movies & music based on my
> declared preferences, but the results were, at best, well, mediocre.
> And so, I'm wondering: has anyone found one of these sites that works
> well? It seems like such a promising idea.
> [1] Most interesting so far: <
http://movielens.umn.edu>
A pet peeve of mine, and part of my job! Caution, long post ahead.
At the CNI fall 05 task force conference, I attended a briefing on the Techlens project that you link to, and there were some interesting observations on when recommenders work, and when they don't (most in the Q&A, so not covered in the abstract).
http://www.cni.org/tfms/2005b.fall/abstracts/PB-techlens-konstan.html
Primary problem of a recommender system is the problem of neighbourhood. How widely do you, as user, want to have the recommendations vary? When you are new to a subject, you want the defining standard works - a narrow view. As you get more versed in the subject, you actually don't want those predictable results anymore, as you will be already familiar with them. Without surprise, it has no value. Different users want different results.
Research on users expectations showed that users were most content with a recommender service if it would give 5 suggestions (in an unobtrusive interface), as long as out of these five one or two would be 'interesting'. Keep in mind though that this was research on users in a strictly defined research field, which can't be translated directly to other fields, but it gives an indication.
How does this translate to amazon? Like Dave, I get the occasional amazon suggestion by email, most of which I delete instantly. Only rarely they were actually interesting. As a result, I find them annoying or amusing, depending on the actual suggestion ;-) However, when I browse amazon, the recommendations are much less obtrusive, so I glance at them when I want, and then I sometimes do find something interesting in there. And I find myself agreeing with the outcome of the techlens research: my amazon miss:hit ratio is 25:1, and I would like more hits, but it needn't be 1:1.
As for the suggestions themselves, they depend on the quality of the data. The ACM techlens used citations to see which objects were linked; Amazon has to rely on more primitive metadata, such as the author. Because it refines this with buying/browsing patterns, it is IMHO actually pretty good, but as with all 'social software' (of which amazon is the granddaddy) this needs a critical mass to get reliable.
Returning to the original question. A good recommender system will always give you some surprising suggestions. It may not always be the surprise you wanted, but if it would be predictable, it would be of no value at all! So by definition, there is a high miss to hit-ratio; therefore, a system must be unobtrusive to not appear, in the words of the original poster, mediocre.
In the long run, this will all change, when the systems will be able to parse the objects (book, movie, etc.) and build relations on the actual content. There is a lot of research in this area, largely spin-off of 'Homeland Security' projects. But it is still years away.
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