Recommender Systems

Synonyms

Recommendation engine

Definition

A recommender system (abbrv. RecSys) is a software artifact that suggests interesting items to users from a large pool of items. Let $\mathcal {U}$ be the set of users registered in the system and $\mathcal {I}$ denote the set of items. RecSys filters items based upon a utility function $\mathcal {F}(u,i)$ that predicts how much a user u (such that $u \in \mathcal {U}$) would like an item i (such that $i \in \mathcal {I}$). The system then recommends a set of items $\mathcal {I}^{\prime }$ such that $\mathcal {I}^{\prime }$ ⊂ $\mathcal {I}$ and $\forall {i \in \mathcal {I}^{\prime }}: \mathcal {F}(u,i) \ge \mathrm {argmax}_{j\in \mathcal {I}-\mathcal {I}^{\prime }}{\mathcal {F}(u,j)}$. In other words, the system selects a set items $\mathcal {I}^{\prime }$ among $\mathcal {I}$ that maximize the recommendation utility function $\mathcal {F}(u,i)$. The cardinality of $\mathcal {I}^{\prime }$ is usually much less than \(\m...