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Recsperts - Recommender Systems Experts

Recsperts - Recommender Systems Experts

Auteur(s): Marcel Kurovski
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 Recommender Systems are the most challenging, powerful and ubiquitous area of machine learning and artificial intelligence. This podcast hosts the experts in recommender systems research and application. From understanding what users really want to driving large-scale content discovery - from delivering personalized online experiences to catering to multi-stakeholder goals. Guests from industry and academia share how they tackle these and many more challenges. With Recsperts coming from universities all around the globe or from various industries like streaming, ecommerce, news, or social media, this podcast provides depth and insights. We go far beyond your 101 on RecSys and the shallowness of another matrix factorization based rating prediction blogpost! The motto is: be relevant or become irrelevant! Expect a brand-new interview each month and follow Recsperts on your favorite podcast player.© 2025 Marcel Kurovski Mathématique Science
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  • #29: Transformers for Recommender Systems with Craig Macdonald and Sasha Petrov

    #29: Transformers for Recommender Systems with Craig Macdonald and Sasha Petrov
    Aug 27 2025
    In episode 29 of Recsperts, I welcome Craig Macdonald, Professor of Information Retrieval at the University of Glasgow, and Aleksandr “Sasha” Petrov, PhD researcher and former applied scientist at Amazon. Together, we dive deep into sequential recommender systems and the growing role of transformer models such as SASRec and BERT4Rec.Our conversation begins with their influential replicability study of BERT4Rec, which revealed inconsistencies in reported results and highlighted the importance of training objectives over architecture tweaks. From there, Craig and Sasha guide us through their award-winning research on making transformers for sequential recommendation with large corpora both more effective and more efficient. We discuss how recency sampling (RSS) reduces training times dramatically, and how gSASRec overcomes the problem of overconfidence in models trained with negative sampling. By generalizing the sigmoid function (gBCE), they were able to reconcile cross-entropy–based optimization results with negative sampling, matching the effectiveness of softmax approaches while keeping training scalable for large corpora.We also explore RecJPQ, their recent work on joint product quantization for item embeddings. This approach makes transformer-based sequential recommenders substantially faster at inference and far more memory-efficient for embeddings—while sometimes even improving effectiveness thanks to regularization effects. Towards the end, Craig and Sasha share their perspective on generative approaches like GPTRec, the promises and limits of large language models in recommendation, and what challenges remain for the future of sequential recommender systems.Enjoy this enriching episode of RECSPERTS – Recommender Systems Experts.Don’t forget to follow the podcast and please leave a review.(00:00) - Introduction(04:09) - About Craig Macdonald(04:46) - About Sasha Petrov(13:48) - Tutorial on Transformers for Sequential Recommendations(19:24) - SASRec vs. BERT4Rec(21:25) - Replicability Study of BERT4Rec for Sequential Recommendation(32:52) - Training Sequential RecSys using Recency Sampling(40:01) - gSASRec for Reducing Overconfidence by Negative Sampling(01:00:51) - RecJPQ: Training Large-Catalogue Sequential Recommenders(01:21:37) - Generative Sequential Recommendation with GPTRec(01:29:12) - Further Challenges and Closing RemarksLinks from the Episode:Craig Macdonald on LinkedInSasha Petrov on LinkedInSasha's WebsiteTutorial: Transformers for Sequential Recommendation (ECIR 2024)Tutorial Recording from ACM European Summer School in Bari (2024)Talk: Neural Recommender Systems (European Summer School in Information Retrieval 2024)Papers:Kang et al. (2018): Self-Attentive Sequential RecommendationSun et al. (2019): BERT4Rec: Sequential Recommendation with Bidirectional Encoder Representations from TransformerPetrov et al. (2022): A Systematic Review and Replicability Study of BERT4Rec for Sequential RecommendationPetrov et al. (2022): Effective and Efficient Training for Sequential Recommendation using Recency SamplingPetrov et al. (2024): RSS: Effective and Efficient Training for Sequential Recommendation Using Recency Sampling (extended version)Petrov et al. (2023): gSASRec: Reducing Overconfidence in Sequential Recommendation Trained with Negative SamplingPetrov et al. (2025): Improving Effectiveness by Reducing Overconfidence in Large Catalogue Sequential Recommendation with gBCE lossPetrov et al. (2024): RecJPQ: Training Large-Catalogue Sequential RecommendersPetrov et al. (2024): Efficient Inference of Sub-Item Id-based Sequential Recommendation Models with Millions of ItemsRajput et al. (2023): Recommender Systems with Generative RetrievalPetrov et al. (2023): Generative Sequential Recommendation with GPTRecPetrov et al. (2024): Aligning GPTRec with Beyond-Accuracy Goals with Reinforcement LearningGeneral Links:Follow me on LinkedInFollow me on XSend me your comments, questions and suggestions to marcel.kurovski@gmail.comRecsperts WebsiteDisclaimer:Craig holds concurrent appointments as a Professor of Information Retrieval at University of Glasgow and as an Amazon Scholar. This podcast describes work performed at the University of Glasgow and is not associated with Amazon.
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    1 h et 37 min
  • #28: Multistakeholder Recommender Systems with Robin Burke

    #28: Multistakeholder Recommender Systems with Robin Burke
    Apr 15 2025
    In episode 28 of Recsperts, I sit down with Robin Burke, professor of information science at the University of Colorado Boulder and a leading expert with over 30 years of experience in recommender systems. Together, we explore multistakeholder recommender systems, fairness, transparency, and the role of recommender systems in the age of evolving generative AI.We begin by tracing the origins of recommender systems, traditionally built around user-centric models. However, Robin challenges this perspective, arguing that all recommender systems are inherently multistakeholder—serving not just consumers as the recipients of recommendations, but also content providers, platform operators, and other key players with partially competing interests. He explains why the common “Recommended for You” label is, at best, an oversimplification and how greater transparency is needed to show how stakeholder interests are balanced.Our conversation also delves into practical approaches for handling multiple objectives, including reranking strategies versus integrated optimization. While embedding multistakeholder concerns directly into models may be ideal, reranking offers a more flexible and efficient alternative, reducing the need for frequent retraining.Towards the end of our discussion, we explore post-userism and the impact of generative AI on recommendation systems. With AI-generated content on the rise, Robin raises a critical concern: if recommendation systems remain overly user-centric, generative content could marginalize human creators, diminishing their revenue streams. Enjoy this enriching episode of RECSPERTS - Recommender Systems Experts.Don't forget to follow the podcast and please leave a review(00:00) - Introduction(03:24) - About Robin Burke and First Recommender Systems(26:07) - From Fairness and Advertising to Multistakeholder RecSys(34:10) - Multistakeholder RecSys Terminology(40:16) - Multistakeholder vs. Multiobjective(42:43) - Reciprocal and Value-Aware RecSys(59:14) - Objective Integration vs. Reranking(01:06:31) - Social Choice for Recommendations under Fairness (01:17:40) - Post-Userist Recommender Systems(01:26:34) - Further Challenges and Closing RemarksLinks from the Episode:Robin Burke on LinkedInRobin's WebsiteThat Recommender Systems LabReference to Broder's Keynote on Computational Advertising and Recommender Systems from RecSys 2008Multistakeholder Recommender Systems (from Recommender Systems Handbook), chapter by Himan Abdollahpouri & Robin BurkePOPROX: The Platform for OPen Recommendation and Online eXperimentationAltRecSys 2024 (Workshop at RecSys 2024)Papers:Burke et al. (1996): Knowledge-Based Navigation of Complex Information SpacesBurke (2002): Hybrid Recommender Systems: Survey and ExperimentsResnick et al. (1997): Recommender SystemsGoldberg et al. (1992): Using collaborative filtering to weave an information tapestryLinden et al. (2003): Amazon.com Recommendations - Item-to-Item Collaborative FilteringAird et al. (2024): Social Choice for Heterogeneous Fairness in RecommendationAird et al. (2024): Dynamic Fairness-aware Recommendation Through Multi-agent Social ChoiceBurke et al. (2024): Post-Userist Recommender Systems : A ManifestoBaumer et al. (2017): Post-userismBurke et al. (2024): Conducting Recommender Systems User Studies Using POPROXGeneral Links:Follow me on LinkedInFollow me on XSend me your comments, questions and suggestions to marcel.kurovski@gmail.comRecsperts Website
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    1 h et 35 min
  • #27: Recommender Systems at the BBC with Alessandro Piscopo and Duncan Walker

    #27: Recommender Systems at the BBC with Alessandro Piscopo and Duncan Walker
    Mar 19 2025

    In episode 27 of Recsperts, we meet Alessandro Piscopo, Lead Data Scientist in Personalization and Search, and Duncan Walker, Principal Data Scientist in the iPlayer Recommendations Team, both from the BBC. We discuss how the BBC personalizes recommendations across different offerings like news or video and audio content recommendations. We learn about the core values for the oldest public service media organization and the collaboration with editors in that process.

    The BBC once started with short video recommendations for BBC+ and nowadays has to consider recommendations across multiple domains: news, the iPlayer, BBC Sounds, BBC Bytesize, and more. With a reach of about 500M+ users who access services every week there is a huge potential. My guests discuss the challenges of aligning recommendations with public service values and the role of editors and constant exchange, alignment, and learning between the algorithmic and editorial lines of recommender systems.
    We also discuss the potential of cross-domain recommendations to leverage the content across different products as well as the organizational setup of teams working on recommender systems at the BBC. We learn about skews in the data due to the nature of an online service that also has a linear offering with TV and radio services.

    Towards the end, we also touch a bit on QUARE @ RecSys, which is the Workshop on Measuring the Quality of Explanations in Recommender Systems.

    Enjoy this enriching episode of RECSPERTS - Recommender Systems Experts.
    Don't forget to follow the podcast and please leave a review

    • (00:00) - Introduction
    • (03:10) - About Alessandro Piscopo and Duncan Walker
    • (14:53) - RecSys Applications at the BBC
    • (20:22) - Journey of Building Public Service Recommendations
    • (28:02) - Role and Implementation of Public Service Values
    • (36:52) - Algorithmic and Editorial Recommendation
    • (01:01:54) - Further RecSys Challenges at the BBC
    • (01:15:53) - Quare Workshop
    • (01:23:27) - Closing Remarks

    Links from the Episode:
    • Alessandro Piscopo on LinkedIn
    • Duncan Walker on LinkedIn
    • BBC
    • QUARE @ RecSys 2023 (2nd Workshop on Measuring the Quality of Explanations in Recommender Systems)

    Papers:

    • Clarke et al. (2023): Personalised Recommendations for the BBC iPlayer: Initial approach and current challenges
    • Boididou et al. (2021): Building Public Service Recommenders: Logbook of a Journey
    • Piscopo et al. (2019): Data-Driven Recommendations in a Public Service Organisation

    General Links:

    • Follow me on LinkedIn
    • Follow me on X
    • Send me your comments, questions and suggestions to marcel.kurovski@gmail.com
    • Recsperts Website
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    1 h et 28 min
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