  In recent years, algorithm research in the area of recommender systems has
shifted from matrix factorization techniques and their latent factor models to
neural approaches. However, given the proven power of latent factor models,
some newer neural approaches incorporate them within more complex network
architectures. One specific idea, recently put forward by several researchers,
is to consider potential correlations between the latent factors, i.e.,
embeddings, by applying convolutions over the user-item interaction map.
However, contrary to what is claimed in these articles, such interaction maps
do not share the properties of images where Convolutional Neural Networks
(CNNs) are particularly useful. In this work, we show through analytical
considerations and empirical evaluations that the claimed gains reported in the
literature cannot be attributed to the ability of CNNs to model embedding
correlations, as argued in the original papers. Moreover, additional
performance evaluations show that all of the examined recent CNN-based models
are outperformed by existing non-neural machine learning techniques or
traditional nearest-neighbor approaches. On a more general level, our work
points to major methodological issues in recommender systems research.
