Horting is a graph-based technique in which nodes are consumers, and edges between nodes indicate degree of similarity between
two consumers (Wolf et al. 1999). Predictions are produced by walking the graph to nearby nodes and combining the opinions of the
nearby consumers. Horting differs from nearest neighbor as the graph may be walked through other consumers who have not rated
the product in question, thus exploring transitive relationships that nearest neighbor algorithms do not consider. In one study using
synthetic data, Horting produced better predictions than a nearest neighbor algorithm (Wolf et al., 1999).
In this paper we review existing e-commerce implementations according to how they are presented to consumers. Most of the Web
stores we review consider the algorithms they use to be proprietary. Many of these algorithms could be used while still presenting
the same interface to the user. For this reason, our taxonomy is based on the basic approach to recommendation, rather than the
specific technology used.