We propose a distributed XML stream filtering system that uses a large number of subscribers' profiles, written in XPath expressions, to filter XML streams and then publish the filtered data in real-time. To realize the proposed system, we define XPath expression features on XML data and utilize them to forecast the servers' loads. Our method is realized by combining methods to share the total transfer loads of each filtering server and to equalize the sum of overlap size between filtering servers. Experiments show that the rate at which the publishing time increases with the number of XPath expressions is three times smaller in the proposed system than in the round-robin method. Furthermore, the overhead of the proposed method is quite low.

This paper proposes an incremental maintenance algorithm that e#ciently updates the materialized XPath/XSLT views defined using XPath expressions in XP{[],*,//,vars}. The algorithm consists of two processes. 1) The dynamic execution flow of an XSLT program is stored as an XT (XML Transformation) tree during the full transformation. 2) In response to a source XML data update, the impacted portions of the XT-tree are identified and maintained by partially re-evaluating the XSLT program. This paper discusses the XPath/XSLT features of incremental view maintenance for subtree insertion/deletion and applies them to the maintenance algorithm. Experiments show that the incremental maintenance algorithm outperforms full XML transformation algorithms by factors of up to 500.