A Tag Recommender System Exploiting User and Community Behavior

Nowadays Web sites tend to be more and more social: users can upload any kind of information on collaborative platforms and can express their opinions about the content they enjoyed through textual feedbacks or reviews. These platforms allow users to annotate resources they like through freely chosen keywords (called tags). The main advantage of these tools is that they perfectly fit user needs, since the use of tags allows organizing the information in a way that closely follows the user mental model, making retrieval of information easier. However, the heterogeneity characterizing the communities causes some problems in the activity of social tagging: someone annotates resources with very specific tags, other people with generic ones, and so on. These drawbacks reduce the exploitation of collaborative tagging systems for retrieval and filtering tasks. Therefore, systems that assist the user in the task of tagging are required. The goal of these systems, called tag recommenders, is to suggest a set of relevant keywords for the resources to be annotated. This paper presents a tag recommender system called STaR (Social Tag Recommender system). Our system is based on two assumptions: 1) the more two or more resources are similar, the more they share common tags 2) a tag recommender should be able to exploit tags the user already used in order to extract useful keywords to label new resources. We also present an experimental evaluation carried out using a large dataset gathered from Bibsonomy.