Time-Variant Factorization Models

All of our proposed factorization models so far do not model any time-variance within factors. In this chapter, we develop a non-parametric approach that allows to model changes in time for each factor. We will focus on the model itself which is generic and not limited to any optimization task like ranking, classification or regression. Even though, factor models for context-aware ranking can benefit from these extensions, this work is not limited to the ranking task, but is more general. That is why we describe the time-aware factorization models for typical problems instead of limiting the discussion to context-aware ranking.