Preferenceaware publish/subscribe delivery with diversity

In publish/subscribe systems, users describe their interests via subscriptions and are notified whenever new interesting events become available. Typically, in such systems, all sub-scriptions are considered equally important. However, due to the abundance of information, users may receive over-whelming amounts of events. In this paper, we propose us-ing a ranking mechanism based on user preferences, so that only top-ranked events are delivered to each user. Since many times top-ranked events are similar to each other, we also propose increasing the diversity of delivered events. Furthermore, we examine a number of different delivering policies for forwarding ranked events to users, namely a pe-riodic, a sliding-window and a history-based one. We have fully implemented our approach in SIENA, a popular pub-lish/subscribe middleware system, and report experimental results of its deployment. 1