Can you clarify what you mean by "recommender systems?"

Dear Virginia Rhodes, Recommender Systems according to Ricci et al., [1] Recommender Systems may be defined as "software tools and techniques providing suggestions for items to be of use to a user. The suggestions relate to various decision-making processes, such as what items to buy, what music to listen to, or what online news to read".

[1] Ricci, F., Rokach, L., & Shapira, B. (2011). Introduction to Recommender Systems Handbook. In Recommender Systems Handbook (pp. 1–35). Springer. https://doi.org/10.1007/978-0-387-85820-3_1

I guess the poster asks about research like

https://ieeexplore.ieee.org/abstract/document/7007848/

but let him clarify.