Reliable retrieval of top-k tags

Abstract

Collaborative tagging systems, such as Flickr and Del.icio.us, allow users to provide keyword labels, or tags, for various Internet resources (e.g., photos, songs, and bookmarks). These tags, which provide a rich source of information, have been used in important applications such as resource searching, webpage clustering, etc. However, tags are provided by casual users, and so their quality cannot be guaranteed. In this paper, we examine a question: given a resource r and a set of user-provided tags associated with r, can r be correctly described by the k most frequent tags? To answer this question, we develop the metric top- k sliding average similarity (top- k SAS) which measures the reliability of k most frequent tags. One threshold is then set to estimate whether the reliability is sufficient for retrieving the top-k tags. Our experiments on real datasets show that the threshold-based evaluation on top-k SAS is effective and efficient to determine whether the k most frequent tags can be considered as high-quality top-k tags for r. Experiments also indicate that setting an appropriate threshold is challenging. The threshold-based strategy is sensitive to a little change of the threshold. To solve this problem, we introduce a parameter-free evaluation strategy that utilizes machine learning models to estimate whether the k most frequent tags are qualified to be the top-k tags. Experiment results demonstrate that the learning-based method achieves comparable performance to the threshold-based method, while overcoming the difficulty of setting a threshold.