770 research outputs found
How to Retrain Recommender System? A Sequential Meta-Learning Method
Practical recommender systems need be periodically retrained to refresh the
model with new interaction data. To pursue high model fidelity, it is usually
desirable to retrain the model on both historical and new data, since it can
account for both long-term and short-term user preference. However, a full
model retraining could be very time-consuming and memory-costly, especially
when the scale of historical data is large. In this work, we study the model
retraining mechanism for recommender systems, a topic of high practical values
but has been relatively little explored in the research community.
Our first belief is that retraining the model on historical data is
unnecessary, since the model has been trained on it before. Nevertheless,
normal training on new data only may easily cause overfitting and forgetting
issues, since the new data is of a smaller scale and contains fewer information
on long-term user preference. To address this dilemma, we propose a new
training method, aiming to abandon the historical data during retraining
through learning to transfer the past training experience. Specifically, we
design a neural network-based transfer component, which transforms the old
model to a new model that is tailored for future recommendations. To learn the
transfer component well, we optimize the "future performance" -- i.e., the
recommendation accuracy evaluated in the next time period. Our Sequential
Meta-Learning(SML) method offers a general training paradigm that is applicable
to any differentiable model. We demonstrate SML on matrix factorization and
conduct experiments on two real-world datasets. Empirical results show that SML
not only achieves significant speed-up, but also outperforms the full model
retraining in recommendation accuracy, validating the effectiveness of our
proposals. We release our codes at: https://github.com/zyang1580/SML.Comment: Appear in SIGIR 202
Lifelong Sequential Modeling with Personalized Memorization for User Response Prediction
User response prediction, which models the user preference w.r.t. the
presented items, plays a key role in online services. With two-decade rapid
development, nowadays the cumulated user behavior sequences on mature Internet
service platforms have become extremely long since the user's first
registration. Each user not only has intrinsic tastes, but also keeps changing
her personal interests during lifetime. Hence, it is challenging to handle such
lifelong sequential modeling for each individual user. Existing methodologies
for sequential modeling are only capable of dealing with relatively recent user
behaviors, which leaves huge space for modeling long-term especially lifelong
sequential patterns to facilitate user modeling. Moreover, one user's behavior
may be accounted for various previous behaviors within her whole online
activity history, i.e., long-term dependency with multi-scale sequential
patterns. In order to tackle these challenges, in this paper, we propose a
Hierarchical Periodic Memory Network for lifelong sequential modeling with
personalized memorization of sequential patterns for each user. The model also
adopts a hierarchical and periodical updating mechanism to capture multi-scale
sequential patterns of user interests while supporting the evolving user
behavior logs. The experimental results over three large-scale real-world
datasets have demonstrated the advantages of our proposed model with
significant improvement in user response prediction performance against the
state-of-the-arts.Comment: SIGIR 2019. Reproducible codes and datasets:
https://github.com/alimamarankgroup/HPM
Considering temporal aspects in recommender systems: a survey
Under embargo until: 2023-07-04The widespread use of temporal aspects in user modeling indicates their importance, and their consideration showed to be highly effective in various domains related to user modeling, especially in recommender systems. Still, past and ongoing research, spread over several decades, provided multiple ad-hoc solutions, but no common understanding of the issue. There is no standardization and there is often little commonality in considering temporal aspects in different applications. This may ultimately lead to the problem that application developers define ad-hoc solutions for their problems at hand, sometimes missing or neglecting aspects that proved to be effective in similar cases. Therefore, a comprehensive survey of the consideration of temporal aspects in recommender systems is required. In this work, we provide an overview of various time-related aspects, categorize existing research, present a temporal abstraction and point to gaps that require future research. We anticipate this survey will become a reference point for researchers and practitioners alike when considering the potential application of temporal aspects in their personalized applications.acceptedVersio
Time-varying Learning and Content Analytics via Sparse Factor Analysis
We propose SPARFA-Trace, a new machine learning-based framework for
time-varying learning and content analytics for education applications. We
develop a novel message passing-based, blind, approximate Kalman filter for
sparse factor analysis (SPARFA), that jointly (i) traces learner concept
knowledge over time, (ii) analyzes learner concept knowledge state transitions
(induced by interacting with learning resources, such as textbook sections,
lecture videos, etc, or the forgetting effect), and (iii) estimates the content
organization and intrinsic difficulty of the assessment questions. These
quantities are estimated solely from binary-valued (correct/incorrect) graded
learner response data and a summary of the specific actions each learner
performs (e.g., answering a question or studying a learning resource) at each
time instance. Experimental results on two online course datasets demonstrate
that SPARFA-Trace is capable of tracing each learner's concept knowledge
evolution over time, as well as analyzing the quality and content organization
of learning resources, the question-concept associations, and the question
intrinsic difficulties. Moreover, we show that SPARFA-Trace achieves comparable
or better performance in predicting unobserved learner responses than existing
collaborative filtering and knowledge tracing approaches for personalized
education
Session-based Recommendation with User Cold-Start Problem Using Markov Chain Model & Incremental Learning
Session-based recommendation has become a hot topic of intelligent system in recent years. As a sub-field of Recommending System, the session-based recommendation studies the sequential relationship of data in user's usage sessions. In some applications, the recommending system should focus more on the personalized usage feature in order to make better recommendations. This thesis analyzed the statistics of user's usage sessions and proposed the Statistics Enhanced FPMC algorithm to enhance the personalized usage pattern of users to improve the recommending performance of recommender system for in-vehicle infotainment system and APP manage system application. The proposed algorithm also addressed the user cold-start problem by incremental learning with a knowledge distillation method to alleviate the catastrophic forgetting problem. The user cold-start problem is defined as making recommendations to new users under cold-start conditions. While the usage data becomes available for new users, the model can continue to be updated to improve recommending performance.MSEElectrical Engineering, College of Engineering & Computer ScienceUniversity of Michigan-Dearbornhttp://deepblue.lib.umich.edu/bitstream/2027.42/167350/1/Zhengru Li - Final Thesis.pd
Dynamic physical activity recommendation on personalised mobile health information service: A deep reinforcement learning approach
Mobile health (mHealth) information service makes healthcare management
easier for users, who want to increase physical activity and improve health.
However, the differences in activity preference among the individual, adherence
problems, and uncertainty of future health outcomes may reduce the effect of
the mHealth information service. The current health service system usually
provides recommendations based on fixed exercise plans that do not satisfy the
user specific needs. This paper seeks an efficient way to make physical
activity recommendation decisions on physical activity promotion in
personalised mHealth information service by establishing data-driven model. In
this study, we propose a real-time interaction model to select the optimal
exercise plan for the individual considering the time-varying characteristics
in maximising the long-term health utility of the user. We construct a
framework for mHealth information service system comprising a personalised AI
module, which is based on the scientific knowledge about physical activity to
evaluate the individual exercise performance, which may increase the awareness
of the mHealth artificial intelligence system. The proposed deep reinforcement
learning (DRL) methodology combining two classes of approaches to improve the
learning capability for the mHealth information service system. A deep learning
method is introduced to construct the hybrid neural network combing long-short
term memory (LSTM) network and deep neural network (DNN) techniques to infer
the individual exercise behavior from the time series data. A reinforcement
learning method is applied based on the asynchronous advantage actor-critic
algorithm to find the optimal policy through exploration and exploitation
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