- [Collaborative filering] (http://en.wikipedia.org/wiki/Collaborative_filtering#Memory-Based) used by amazon
- a graph based movie recommender engine
- [Wikipedia definition] (http://en.wikipedia.org/wiki/Graph_database)
- [Empirical Analysis of Predictive Algorithms for Collaborative Filtering] (http://research.microsoft.com/pubs/69656/tr-98-12.pdf) at Microsoft Research