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From Tolga Oral <>
Subject Re: Recommending items for anonymous users
Date Tue, 20 Apr 2010 20:25:27 GMT
For the application I am working on we have similar problem that we are
trying solve in different ways. Our users are not anonymous but some of them
have no preference data (user ---> item link).

PlusAnonymousUserDataModel will work once the user clicks on couple items on
the site, however still doesnt solve the dead-start problem. We are creating
user similarities based on different attributes and use the similarities to
recommend items (doesn't solve all cases though)

However I am still interested in figuring out the most popular items with
some diversity (otherwise new "interesting/good" items have no chance of
ever getting in recommendations) ? Any ideas how we can do this in mahout?

> Responses inline.
> Yep, I know what you mean. I didn't really talk about this (yet) in
> > the book and likely should spend a page on it.
> >
> That would be great. I mean, the two discovery problems are 'user'
> discovery
> and 'item' discovery. Using content-based approaches, I can do something
> about when to recommend a new item... but the user approach example would
> be
> great.
> Of course, I wouldn't want to talk you out of documenting the best-practice
> for Mahout based item discovery in the final version of the book.
> > One solution is to punt on the problem, as Ted says: until you get
> > enough data or the user has a real presence, don't recommend.
> >
> In my case, this isn't practical. For now, (and in my home grown,
> deprecated
> recommender) I have a "backfill list" (built with system-wide stats) that I
> use to make a recommendation when I can't come up with anything from my
> existing recommender... but the main point of my email was that I may want
> to get rid of this and do as much as possible inside of Mahout.
> > ...
> >
> > I can offer you a mildly hacky but fairly useful middle-ground:
> > PlusAnonymousUserDataModel. It decorates/wraps your DataModel and lets
> > you temporarily set preferences for one anonymous new user. (You need
> > to think of thread-safety potentially -- you can only do this for one
> > user at a time.)
> >
> >
> This would be ideal. I will be using a default userid of 0 for anonymous
> users, and as far as the application is concerned, I can treat all
> anonymous
> users as the same anonymous user for now.
> ...
> >
> Appreciated.

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