Abstract. In this paper we address the problem of subsumption checking for subscriptions in pub/sub systems. We develop a novel approach based on negative space representation for subsumption checking and provide efficient algorithms for subscription forwarding in a dynamic pub/ sub environment. We then provide heuristics for approximate subsumption checking that greatly enhance the performance without compromising the correct execution of the system and only adding incremental cost in terms of extra computation in brokers. We illustrate the advantages of this novel approach by carrying out extensive experimentation. Keywords: Publish/Subscribe, Subscription Subsumption, Messageoriented middleware. 1

Abstract — Subscription covering detection is useful to improving the performance of any publish/subscribe system. However, an exact solution to querying coverings among a large set of subscriptions in high dimension is computationally too expensive to be practicable. Therefore, we are interested in an approximate approach. We focus on spherical subscriptions and propose a solution based on random projections. Our complexities are substantially better than that of the exact approach. The proposed solution can potentially find exact coverings with a success probability 100 % asymptotically approachable. I.

One of the main challenges faced by content-based publish/subscribe systems is handling large amount of dynamic subscriptions and publications in a multidimensional content space. To reduce subscription forwarding load and speed up content matching, subscription covering, subsumption and merging techniques have been proposed. In this paper we propose MICS, Multidimensional Indexing for Content Space that provides an efficient representation and processing model for large number of subscriptions and publications. MICS creates a one dimensional representation for publications and subscriptions using Hilbert space filling curve. Based on this representation, we propose novel content matching and subscription management (covering, subsumption and merging) algorithms. Our experimental evaluation indicates that the proposed approach significantly speeds up subscription management operations compared to the naive linear approach.