In this paper, we investigate recommender systems from a network perspective and investigate recommendation networks, where nodes are items (e.g., movies) and edges are constructed from top-N recommendations (e.g., related movies). In particular, we focus on evaluating the reachability and navigability of recommendation networks and investigate the following questions: (i) How well do recommendation networks support navigation and exploratory search? (ii) What is the influence of parameters, in particular different recommendation algorithms and the number of recommendations shown, on reachability and navigability? and (iii) How can reachability and navigability be improved in these networks? We tackle these questions by first evaluating the reachability of recommendation networks by investigating their structural properties. Second, we evaluate navigability by simulating three different models of information seeking scenarios. We find that with standard algorithms, recommender systems are not well suited to navigation and exploration and propose methods to modify recommendations to improve this. Our work extends from one-click-based evaluations of recommender systems towards multi-click analysis (i.e., sequences of dependent clicks) and presents a general, comprehensive approach to evaluating navigability of arbitrary recommendation networks.
A simple method to improve reachability is to select recommendations specifically for their target in the network, which has been proposed by @cite_14 . In this work, we improve on this method by proposing a method that not only improves reachability but also ensures the relevance of the selected recommendations.
@cite_14
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Many music portals offer the possibility to explore music collections via browsing automatically generated music recommendations. In this paper we argue that such music recommender systems can be transformed into an equivalent recommendation graph. We then analyze the recommendation graph of a real-world content-based music recommender systems to find out if users can really explore the underlying song database by following those recommendations. We find that some songs are not recommended at all and are consequently not reachable via browsing. We then take a first attempt to modify a recommendation network in such a way that the resulting network is better suited to explore the respective music space.