Emmanuel Filiot, Joachim Niehren, Jean-Marc Talbot, Sophie Tison. Polynomial time fragments of XPath with variables. In Leonid Libkin, editor, Proceedings of the Twenty-Sixth ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems, June 11-13, 2007, Beijing, China. pages 205-214, ACM, 2007. [doi]
Abstract is missing.