11 research outputs found
Alleviating Behavior Data Imbalance for Multi-Behavior Graph Collaborative Filtering
Graph collaborative filtering, which learns user and item representations
through message propagation over the user-item interaction graph, has been
shown to effectively enhance recommendation performance. However, most current
graph collaborative filtering models mainly construct the interaction graph on
a single behavior domain (e.g. click), even though users exhibit various types
of behaviors on real-world platforms, including actions like click, cart, and
purchase. Furthermore, due to variations in user engagement, there exists an
imbalance in the scale of different types of behaviors. For instance, users may
click and view multiple items but only make selective purchases from a small
subset of them. How to alleviate the behavior imbalance problem and utilize
information from the multiple behavior graphs concurrently to improve the
target behavior conversion (e.g. purchase) remains underexplored. To this end,
we propose IMGCF, a simple but effective model to alleviate behavior data
imbalance for multi-behavior graph collaborative filtering. Specifically, IMGCF
utilizes a multi-task learning framework for collaborative filtering on
multi-behavior graphs. Then, to mitigate the data imbalance issue, IMGCF
improves representation learning on the sparse behavior by leveraging
representations learned from the behavior domain with abundant data volumes.
Experiments on two widely-used multi-behavior datasets demonstrate the
effectiveness of IMGCF.Comment: accepted by ICDM2023 Worksho
Multi-Behavior Hypergraph-Enhanced Transformer for Sequential Recommendation
Learning dynamic user preference has become an increasingly important
component for many online platforms (e.g., video-sharing sites, e-commerce
systems) to make sequential recommendations. Previous works have made many
efforts to model item-item transitions over user interaction sequences, based
on various architectures, e.g., recurrent neural networks and self-attention
mechanism. Recently emerged graph neural networks also serve as useful backbone
models to capture item dependencies in sequential recommendation scenarios.
Despite their effectiveness, existing methods have far focused on item sequence
representation with singular type of interactions, and thus are limited to
capture dynamic heterogeneous relational structures between users and items
(e.g., page view, add-to-favorite, purchase). To tackle this challenge, we
design a Multi-Behavior Hypergraph-enhanced Transformer framework (MBHT) to
capture both short-term and long-term cross-type behavior dependencies.
Specifically, a multi-scale Transformer is equipped with low-rank
self-attention to jointly encode behavior-aware sequential patterns from
fine-grained and coarse-grained levels. Additionally, we incorporate the global
multi-behavior dependency into the hypergraph neural architecture to capture
the hierarchical long-range item correlations in a customized manner.
Experimental results demonstrate the superiority of our MBHT over various
state-of-the-art recommendation solutions across different settings. Further
ablation studies validate the effectiveness of our model design and benefits of
the new MBHT framework. Our implementation code is released at:
https://github.com/yuh-yang/MBHT-KDD22.Comment: Published as a KDD'22 full pape
Revisiting Initializing Then Refining: An Incomplete and Missing Graph Imputation Network
With the development of various applications, such as social networks and
knowledge graphs, graph data has been ubiquitous in the real world.
Unfortunately, graphs usually suffer from being absent due to
privacy-protecting policies or copyright restrictions during data collection.
The absence of graph data can be roughly categorized into attribute-incomplete
and attribute-missing circumstances. Specifically, attribute-incomplete
indicates that a part of the attribute vectors of all nodes are incomplete,
while attribute-missing indicates that the whole attribute vectors of partial
nodes are missing. Although many efforts have been devoted, none of them is
custom-designed for a common situation where both types of graph data absence
exist simultaneously. To fill this gap, we develop a novel network termed
Revisiting Initializing Then Refining (RITR), where we complete both
attribute-incomplete and attribute-missing samples under the guidance of a
novel initializing-then-refining imputation criterion. Specifically, to
complete attribute-incomplete samples, we first initialize the incomplete
attributes using Gaussian noise before network learning, and then introduce a
structure-attribute consistency constraint to refine incomplete values by
approximating a structure-attribute correlation matrix to a high-order
structural matrix. To complete attribute-missing samples, we first adopt
structure embeddings of attribute-missing samples as the embedding
initialization, and then refine these initial values by adaptively aggregating
the reliable information of attribute-incomplete samples according to a dynamic
affinity structure. To the best of our knowledge, this newly designed method is
the first unsupervised framework dedicated to handling hybrid-absent graphs.
Extensive experiments on four datasets have verified that our methods
consistently outperform existing state-of-the-art competitors
Causal Inference in Recommender Systems: A Survey and Future Directions
Recommender systems have become crucial in information filtering nowadays.
Existing recommender systems extract user preferences based on the correlation
in data, such as behavioral correlation in collaborative filtering,
feature-feature, or feature-behavior correlation in click-through rate
prediction. However, unfortunately, the real world is driven by causality, not
just correlation, and correlation does not imply causation. For instance,
recommender systems might recommend a battery charger to a user after buying a
phone, where the latter can serve as the cause of the former; such a causal
relation cannot be reversed. Recently, to address this, researchers in
recommender systems have begun utilizing causal inference to extract causality,
thereby enhancing the recommender system. In this survey, we offer a
comprehensive review of the literature on causal inference-based
recommendation. Initially, we introduce the fundamental concepts of both
recommender system and causal inference as the foundation for subsequent
content. We then highlight the typical issues faced by non-causality
recommender system. Following that, we thoroughly review the existing work on
causal inference-based recommender systems, based on a taxonomy of three-aspect
challenges that causal inference can address. Finally, we discuss the open
problems in this critical research area and suggest important potential future
works.Comment: Accepted by ACM Transactions on Information Systems (TOIS
Advances and Challenges of Multi-task Learning Method in Recommender System: A Survey
Multi-task learning has been widely applied in computational vision, natural
language processing and other fields, which has achieved well performance. In
recent years, a lot of work about multi-task learning recommender system has
been yielded, but there is no previous literature to summarize these works. To
bridge this gap, we provide a systematic literature survey about multi-task
recommender systems, aiming to help researchers and practitioners quickly
understand the current progress in this direction. In this survey, we first
introduce the background and the motivation of the multi-task learning-based
recommender systems. Then we provide a taxonomy of multi-task learning-based
recommendation methods according to the different stages of multi-task learning
techniques, which including task relationship discovery, model architecture and
optimization strategy. Finally, we raise discussions on the application and
promising future directions in this area
Recommending on graphs: a comprehensive review from a data perspective
Recent advances in graph-based learning approaches have demonstrated their
effectiveness in modelling users' preferences and items' characteristics for
Recommender Systems (RSS). Most of the data in RSS can be organized into graphs
where various objects (e.g., users, items, and attributes) are explicitly or
implicitly connected and influence each other via various relations. Such a
graph-based organization brings benefits to exploiting potential properties in
graph learning (e.g., random walk and network embedding) techniques to enrich
the representations of the user and item nodes, which is an essential factor
for successful recommendations. In this paper, we provide a comprehensive
survey of Graph Learning-based Recommender Systems (GLRSs). Specifically, we
start from a data-driven perspective to systematically categorize various
graphs in GLRSs and analyze their characteristics. Then, we discuss the
state-of-the-art frameworks with a focus on the graph learning module and how
they address practical recommendation challenges such as scalability, fairness,
diversity, explainability and so on. Finally, we share some potential research
directions in this rapidly growing area.Comment: Accepted by UMUA