An efficient subscription routing algorithm for scalable XML-based publish/subscribe systems

XML-based publish/subscribe systems have gained popularity as one of the newly emerging communication paradigms. As the number of clients has increased, the concept of the scalability has become the most important factor in the distributed information processing. In this paper, we propose an efficient subscription routing algorithm as a part of efforts to achieve scalability, with subscriptions especially expressed in XPath patterns. We first discuss that the homomorphism relationship among XPath patterns can be utilized for routing XPath patterns. Then, we develop a lattice data structure called the partially ordered set of XPath patterns which is abbreviated as POX and its corresponding algorithm for efficiently maintaining homomorphism relationships. Finally, we present performance evaluation results which validate our algorithm with respect to system performance and scalability.