8,691 research outputs found
Context-Aware Rank-Oriented Recommender Systems
abstract: Recommender systems are a type of information filtering system that suggests items that may be of interest to a user. Most information retrieval systems have an overwhelmingly large number of entries. Most users would experience information overload if they were forced to explore the full set of results. The goal of recommender systems is to overcome this limitation by predicting how users will value certain items and returning the items that should be of the highest interest to the user. Most recommender systems collect explicit user feedback, such as a rating, and attempt to optimize their model to this rating value. However, there is potential for a system to collect implicit user feedback, such as user purchases and clicks, to learn user preferences. Additionally with implicit user feedback, it is possible for the system to remember the context of user feedback in terms of which other items a user was considering when making their decisions. When considering implicit user feedback, only a subset of all evaluation techniques can be used. Currently, sufficient evaluation techniques for evaluating implicit user feedback do not exist. In this thesis, I introduce a new model for recommendation that borrows the idea of opportunity cost from economics. There are two variations of the model, one considering context and one that does not. Additionally, I propose a new evaluation measure that works specifically for the case of implicit user feedback.Dissertation/ThesisM.S. Computer Science 201
PrivateJobMatch: A Privacy-Oriented Deferred Multi-Match Recommender System for Stable Employment
Coordination failure reduces match quality among employers and candidates in
the job market, resulting in a large number of unfilled positions and/or
unstable, short-term employment. Centralized job search engines provide a
platform that connects directly employers with job-seekers. However, they
require users to disclose a significant amount of personal data, i.e., build a
user profile, in order to provide meaningful recommendations. In this paper, we
present PrivateJobMatch -- a privacy-oriented deferred multi-match recommender
system -- which generates stable pairings while requiring users to provide only
a partial ranking of their preferences. PrivateJobMatch explores a series of
adaptations of the game-theoretic Gale-Shapley deferred-acceptance algorithm
which combine the flexibility of decentralized markets with the intelligence of
centralized matching. We identify the shortcomings of the original algorithm
when applied to a job market and propose novel solutions that rely on machine
learning techniques. Experimental results on real and synthetic data confirm
the benefits of the proposed algorithms across several quality measures. Over
the past year, we have implemented a PrivateJobMatch prototype and deployed it
in an active job market economy. Using the gathered real-user preference data,
we find that the match-recommendations are superior to a typical decentralized
job market---while requiring only a partial ranking of the user preferences.Comment: 45 pages, 28 figures, RecSys 201
Recommender Systems by means of Information Retrieval
In this paper we present a method for reformulating the Recommender Systems
problem in an Information Retrieval one. In our tests we have a dataset of
users who give ratings for some movies; we hide some values from the dataset,
and we try to predict them again using its remaining portion (the so-called
"leave-n-out approach"). In order to use an Information Retrieval algorithm, we
reformulate this Recommender Systems problem in this way: a user corresponds to
a document, a movie corresponds to a term, the active user (whose rating we
want to predict) plays the role of the query, and the ratings are used as
weigths, in place of the weighting schema of the original IR algorithm. The
output is the ranking list of the documents ("users") relevant for the query
("active user"). We use the ratings of these users, weighted according to the
rank, to predict the rating of the active user. We carry out the comparison by
means of a typical metric, namely the accuracy of the predictions returned by
the algorithm, and we compare this to the real ratings from users. In our first
tests, we use two different Information Retrieval algorithms: LSPR, a recently
proposed model based on Discrete Fourier Transform, and a simple vector space
model
Optimal Pricing with Recommender Systems
We study optimal pricing in the presence of recommender systems. A recommender system affects the market in two ways: (i) it creates value by reducing product uncertainty for the customers and hence (ii) its recommendations can be offered as add-ons which generate informational externalities. The quality of the recommendation add-on is endogenously determined by sales. We investigate the impact of these factors on the optimal pricing by a seller with a recommender system against a competitive fringe without such a system. If the recommender system is sufficiently effective in reducing uncertainty, then the seller prices otherwise symmetric products differently to have some products experienced more aggressively. Moreover, the seller segments the market so that customers with more inflexible tastes pay higher prices to get better recommendations.Recommender system, Collaborative filtering, Add-ons, Pricing, Information externality
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