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From Christoph Hermann <>
Subject Re: store time in DataModel
Date Fri, 25 Jun 2010 06:37:45 GMT
Am Freitag, 25. Juni 2010 00:43:50 schrieb Tamas Jambor:


> >> Just wondering if there is an option to store time in one of the
> >> DataModels? Looking at the code, it looks this is not implemented
> >> yet.

> > No, this is not really part of collaborative filtering per se. But
> > nothing about the model precludes you from storing and using time
> > -- it's just not relevant to the core CF algorithm. For example
> > you're welcome to have a timestamp column in your database table
> > alongside other columns, doesn't matter.

> thanks. I don't really agree that it's not relevant, though. Many new
> methods are beginning to integrate temporal dynamics into the models.

I totally agree on that.
What about changing Mahouts core code to be able to implement this more 

I thought about having an Interface that could be extended depending 
which data you have. Since you (almost) always have Users and Items, 
that should be default and then additional interfaces could add either 
ratings or timestamps (or both) and then extend the code this way.
Also separating User and Item based recommenders would remove the need 
to throw UnsupportedOperationExceptions (just a thought).

I've implemented a recommender for learning environments which is 
completely based on timestamps, I'll present it at the upcoming AACE Ed-
Media in Toronto.
The basic idea is that when users behave the same way over time, you can 
use timestamps of items and their relations to create recommendations.
So yes, i think there are settings where timestamps are worth to be 

Christoph Hermann

Christoph Hermann
Institut für Informatik
Tel: +49 761-203-8171 Fax: +49 761-203-8162

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