This paper proposes an incremental maintenance algorithm that efficiently 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. Categories and Subject Descriptors H.2.3 [DATABASE MANAGEMENT]: Languages; D.3. 4 [PROGRAMMING LANGUAGES]: Processors—Optimization General Terms Algorithms, Languages, Performance Keywords XML, XPath, XSLT, mater...