|Talks|

Revisiting Representation Learning in Complex Networks with Applications to Recommender Systems

Dissertation proposal
Hybrid
Past Talk
David Liu
PhD Candidate in the Khoury College of Computer Sciences
Fri, Mar 21, 2025
4:30 PM UTC
Fri, Mar 21, 2025
4:30 PM UTC
In-person
4 Thomas More St
London E1W 1YW, UK
The Roux Institute
Room
100 Fore Street
Portland, ME 04101
Network Science Institute
11th floor
177 Huntington Ave
Boston, MA 02115
Room
58 St Katharine's Way
London E1W 1LP, UK

Talk recording

Increasingly, training machine learning models requires the compression of vast amounts of data and perspectives. For instance, when learning on social networks, the interactions between people are compressed into a low-dimensional space. Effective machine learning models necessitate efficient, stable, and fair representation; this dissertation identifies challenges and algorithms for achieving such representations for complex networks. First, I present work tackling the technical challenge of learning embeddings efficiently and stably. I demonstrate how we can reduce the memory footprint of graph representation learning by considering more efficient alternatives to negative sampling utilizing dimension regularization. I also identify instability in current graph embedding algorithms to perturbations in the periphery of the network and present a meta-algorithm for mitigating such instability. Second, I show that graph representation learning broadens our approach to and understanding of algorithmic fairness. Graph representation learning enables us to measure group fairness without discrete class labels, and analyzing embeddings elicits mechanisms of unfairness in collaborative filtering. To conclude, I propose work on mitigating popularity bias in recommender systems. It is known that recommender systems learn better representations for popular items, resulting in a feedback loop of less and less diverse recommendations. I propose utilizing regularization techniques from degree-corrected network models, which have been shown to improve group inference in popularity-heterogeneous networks, to improve the representation of low-resource users and items.

About the speaker
David Liu is a final-year computer science Ph.D. candidate at Northeastern University advised by Professor Tina Eliassi-Rad. His research lies at the intersection of graph machine learning, algorithmic fairness, and the societal impacts of AI with publications at SIAM SDM, FAccT, and AIES. He has interned twice at Meta (Central Applied Science and FAIR AI) and has consulted as a sociotechnical researcher at the non-profit Taraaz. David obtained a Bachelors in Computer Science from Princeton University. His work is supported by the NSF GRFP.
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Mar 21, 2025