Hierarchical Transformer with Spatio-Temporal Context Aggregation for Next Point-of-Interest Recommendation

Next point-of-interest (POI) recommendation is a critical task in location-based social networks, yet remains challenging due to a high degree of variation and personalization exhibited in user movements. In this work, we explore the latent hierarchical structure composed of multi-granularity short-term structural patterns in user check-in sequences. We propose a Spatio-Temporal context AggRegated Hierarchical Transformer (STAR-HiT) for next POI recommendation, which employs stacked hierarchical encoders to recursively encode the spatio-temporal context and explicitly locate subsequences of different granularities. More specifically, in each encoder, the global attention layer captures the spatio-temporal context of the sequence, while the local attention layer performed within each subsequence enhances subsequence modeling using the local context. The sequence partition layer infers positions and lengths of subsequences from the global context adaptively, such that semantics in subsequences can be well preserved. Finally, the subsequence aggregation layer fuses representations within each subsequence to form the corresponding subsequence representation, thereby generating a new sequence of higher-level granularity. The stacking of encoders captures the latent hierarchical structure of the check-in sequence, which is used to predict the next visiting POI. Extensive experiments on three public datasets demonstrate that the proposed model achieves superior performance whilst providing explanations for recommendations. Codes are available at https://github.com/JennyXieJiayi/STAR-HiT

Multi-Relational Contrastive Learning for Recommendation

Personalized recommender systems play a crucial role in capturing users' evolving preferences over time to provide accurate and effective recommendations on various online platforms. However, many recommendation models rely on a single type of behavior learning, which limits their ability to represent the complex relationships between users and items in real-life scenarios. In such situations, users interact with items in multiple ways, including clicking, tagging as favorite, reviewing, and purchasing. To address this issue, we propose the Relation-aware Contrastive Learning (RCL) framework, which effectively models dynamic interaction heterogeneity. The RCL model incorporates a multi-relational graph encoder that captures short-term preference heterogeneity while preserving the dedicated relation semantics for different types of user-item interactions. Moreover, we design a dynamic cross-relational memory network that enables the RCL model to capture users' long-term multi-behavior preferences and the underlying evolving cross-type behavior dependencies over time. To obtain robust and informative user representations with both commonality and diversity across multi-behavior interactions, we introduce a multi-relational contrastive learning paradigm with heterogeneous short- and long-term interest modeling. Our extensive experimental studies on several real-world datasets demonstrate the superiority of the RCL recommender system over various state-of-the-art baselines in terms of recommendation accuracy and effectiveness.Comment: This paper has been published as a full paper at RecSys 202

A personality aware recommendation system

Les systèmes de recommandation conversationnels (CRSs) sont des systèmes qui fournissent des recommandations personnalisées par le biais d’une session de dialogue en langage naturel avec les utilisateurs. Contrairement aux systèmes de recommandation traditionnels qui ne prennent comme vérité de base que les préférences anciennes des utilisateurs, les CRS impliquent aussi les préférences actuelles des utilisateurs durant la conversation. Des recherches récentes montrent que la compréhension de la signification contextuelle des préférences des utilisateurs et des dialogues peut améliorer de manière significative les performances du système de recommandation. Des chercheurs ont également montré un lien fort entre les traits de personnalité des utilisateurs et les systèmes de recommandation. La personnalité et les préférences sont des variables essentielles en sciences sociales. Elles décrivent les différences entre les personnes, que ce soit au niveau individuel ou collectif. Les approches récentes de recommandation basées sur la personnalité sont des systèmes non conversationnels. Par conséquent, il est extrêmement important de détecter et d’utiliser les traits de personnalité des individus dans les systèmes conversationnels afin d’assurer une performance de recommandation et de dialogue plus personnalisée. Pour ce faire, ce travail propose un système de recommandation conversationnel sensible à la personnalité qui est basé sur des modules qui assurent une session de dialogue et recommandation personnalisée en utilisant les traits de personnalité des utilisateurs. Nous proposons également une nouvelle approche de détection de la personnalité, qui est un modèle de langage spécifique au contexte pour détecter les traits des individus en utilisant leurs données publiées sur les réseaux sociaux. Les résultats montrent que notre système proposé a surpassé les approches existantes dans différentes mesures.A Conversational Recommendation System (CRS) is a system that provides personalized recommendations through a session of natural language dialogue turns with users. Unlike traditional one-shot recommendation systems, which only assume the user’s previous preferences as the ground truth, CRS uses both previous and current user preferences. Recent research shows that understanding the contextual meaning of user preferences and dialogue turns can significantly improve recommendation performance. It also shows a strong link between users’ personality traits and recommendation systems. Personality and preferences are essential variables in computational sociology and social science. They describe the differences between people, both at the individual and collective level. Recent personality-based recommendation approaches are traditional one-shot systems, or “non conversational systems”. Therefore, there is a significant need to detect and employ individuals’ personality traits within the CRS paradigm to ensure a better and more personalized dialogue recommendation performance. Driven by the aforementioned facts, this study proposes a modularized, personality- aware CRS that ensures a personalized dialogue recommendation session using the users’ personality traits. We also propose a novel personality detection approach, which is a context-specific language model for detecting individuals’ personality traits using their social media data. The goal is to create a personality-aware and topic-guided CRS model that performs better than the standard CRS models. Experimental results show that our personality-aware conversation recommendation system has outperformed state-of-the-art approaches in different considered metrics on the topic-guided conversation recommendation dataset