On Processing and Notifying Range Top-k Subscriptions

The authors consider how to support a large number of range top-k subscriptions for wide-area publish/subscribe. Given an object update, they need to notify subscriptions whose top-k results are affected. Simple solutions include using a content-driven network to notify all subscriptions whose ranges contain the update (ignoring top-k), or using a server to compute only the affected subscriptions and notifying them individually. The former solution generates too much network traffic, while the latter overwhelms the server. The authors present a geometric framework for the problem that allows people to describe the set of affected subscriptions succinctly with messages that can be efficiently disseminated using content-driven networks.