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From Anatoliy Kats <>
Subject Re: New feature idea: Eligible Items for recommendations
Date Tue, 15 Nov 2011 11:55:41 GMT
Duh!  Thanks:)  I can't feed a rescorer to the evaluator, but I can work 
around that:  I am already creating my own recommender class by 
subclassing the ItemBasedRecommender, so I can just overload the 
recommend(..) to super.recommend(.., IDRescorer).  It seems like a more 
elegant solution than adding the rescorer to the evaluator.

On 11/15/2011 03:38 PM, Sean Owen wrote:
> This is exactly what Rescorer is for in the recommend() method. Does that
> suit?
> On Nov 15, 2011 11:37 AM, "Anatoliy Kats"<>  wrote:
>> Hi all,
>> I have a use case for Taste where we should use all available items for
>> computation of user similarity, but only some items are eligible to be
>> recommended.  The reason is that items expire:  goods get discontinued, for
>> example.  The fact that a user bought something now discontinued is
>> important for finding similar users, but we cannot recommend it.  One way
>> of solving this is using mahout to generate recommendations, and then
>> post-process it to remove ineligible items.  But this can run into
>> performance issues if the set of ineligible items is large.  Also, the
>> evaluation framework is not designed to handle this kind of a restriction.
>> I can contribute a patch, but since I am new to the project, I need some
>> help with the software engineering from the regular contributors.  How
>> would I design the necessary classes?  One idea I considered was using the
>> existing tools for candidate item strategy.  This has two downsides:  you
>> can only use one candidate item strategy at a time, so having an eligible
>> set would make it impossible to have a candidate item strategy.  Also, the
>> evaluator doesn't take the candidate item strategy into account.  So, I
>> suppose I could try writing an EligibleSetCandidateItemStrate**gy that
>> takes another CandidateItemStrategy and applies it as well, and I can add a
>> new evaluator that takes eligible sets into account.  I don't know the
>> thinking behind the design, so I don't know if this is a good idea or not.
>>   Can we agree on a design before I get started?
>> Cheers,
>> Anatoliy

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