Azure Machine Learning has an item called Train Matchbox Recommender. It can be configured with a Number of traits. Unfortunately, the documentation does not describe what such a trait is.
What are traits? Is this related to latent variables?
This page may have better descriptions on it.
Basically, traits are the features the algorithm will learn about each user related to each item. For example, in the restaurant ratings recommender traits could include a user's birth year, if they're a student or working professional, martial status, etc.
Hope that helps!