Some recommenders, such as those on news sites, will want to provide recommenders that incorporate content analysis as well as
preference analysis. Many machine-learning techniques have been shown to effectively build a model of human preferences based on
content. Information filtering systems (Salton, 1968) build models of customer preferences based on keyword vectors. Other systems
employ neural networks and other feedback systems to learn preference patterns. While these systems cannot entirely replace the
human values captured in collaborative filtering systems, there is evidence that they can augment collaborative filtering. Other
approaches combine machine-learning techniques with collaborative filtering ones.