A Counterfactual Collaborative Session-based Recommender System

TL;DR

This paper introduces COCO-SBRS, a novel session-based recommender system that incorporates causal inference to address the influence of outside-session causes, improving recommendation accuracy by learning true causal relationships.

Contribution

It proposes a causal inference framework for SBRSs that models outside-session causes, using self-supervised pre-training and counterfactual inference to reduce spurious correlations.

Findings

COCO-SBRS outperforms ten baseline SBRS models on three real-world datasets.

The framework effectively learns causal relationships, reducing bias from confounders.

Experimental results demonstrate improved recommendation accuracy and robustness.

Abstract

Most session-based recommender systems (SBRSs) focus on extracting information from the observed items in the current session of a user to predict a next item, ignoring the causes outside the session (called outer-session causes, OSCs) that influence the user's selection of items. However, these causes widely exist in the real world, and few studies have investigated their role in SBRSs. In this work, we analyze the causalities and correlations of the OSCs in SBRSs from the perspective of causal inference. We find that the OSCs are essentially the confounders in SBRSs, which leads to spurious correlations in the data used to train SBRS models. To address this problem, we propose a novel SBRS framework named COCO-SBRS (COunterfactual COllaborative Session-Based Recommender Systems) to learn the causality between OSCs and user-item interactions in SBRSs. COCO-SBRS first adopts a self-supervised approach to pre-train a recommendation model by designing pseudo-labels of causes for each user's selection of the item in data to guide the training process. Next, COCO-SBRS adopts counterfactual inference to recommend items based on the outputs of the pre-trained recommendation model considering the causalities to alleviate the data sparsity problem. As a result, COCO-SBRS can learn the causalities in data, preventing the model from learning spurious correlations. The experimental results of our extensive experiments conducted on three real-world datasets demonstrate the superiority of our proposed framework over ten representative SBRSs.