An XML Publish/Subscribe Algorithm Implemented by Relational Operators

An XML publish/subscribe algorithm needs to store large numbers of XPath or XQuery subscriptions and match subscriptions with published XML documents. Since the number of the subscriptions may be very large, the performance and the scalability of the algorithm may be critical. The scalability of the method of constructing a large finite state automata or decision tree for all subscriptions is limited by amount of available physical memory. In this paper, we will introduce an XML publish/subscribe algorithm which is consisted of the publish algorithm, subscribe algorithm, and matching algorithm. The matching algorithm uses relational operators to match subscriptions with publications inside a relational database, so the scalability of the algorithm is no longer limited by amount of available physical memory. Experimental results show that the matching algorithm has very good performance and scalability.

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